When she had gone the rest of them sat silent. Dr Fell was wheezing sleepily. And again Hadley began to pace about.

'So that's settled, he said. `I think we can take Mrs Bitton off the list of suspects. I doubt if Larkin's lying. Her in formation is too exactly in line with all the other facts she couldn't possibly have known. Now what?'

'What do you suggest?'

`It all rests on what it was Driscoll remembered he'd forgotten to do when he spoke to Mrs Bitton in front of the Traitors' Gate. He started for somewhere, but he didn't get very far away, and then he ran into somebody…. the murderer.'

`Fair enough,' grunted the doctor.

`Now, first, there's the direction he, might have gone.' Larkin didn't see him go. But we know he didn't go along Water Lane towards the Byward or Middle Tower; towards the gate, in other words. Because Larkin was standing there, and she would have seen him pass.

`There are only two other directions he could have gone. He could have gone straight, along Water Lane in the other direction. The only place he could have gone in that direction is towards another arch, similar to the Bloody Tower and a hundred feet or so away in the same wall the inner ballium wall. From that arch a path leads up to the White Tower, which is almost in the centre of the whole enclosure. Now, unless all our calculations are wrong, and there's some piece of evidence we haven't heard, why on earth should he be going to the White Tower? Or, for that matter, to the main guard, the store, the hospital, or any place he could have reached by going through the arch?

`Besides, he hadn't got very far away from the Traitors' Gate before he met the murderer. Traitors' Gate is an ideal place for murder on a foggy day. But if Driscoll had been starting for the White Tower and met the murderer quite some distance from Traitors' Gate, it wouldn't have been very practical for the murderer to drive that steel bolt through him, pick him up, carry him back, and pitch him over the rail. The risk of being seen carrying that burden any distance, even in the fog, would have been too great.'

Hadley paused in his pacing before the mantelpiece.,

`On the other hand, the murderer couldn't say,"Look here, old man, let's stroll back to the Traitors' Gate I want to talk to you." Naturally Driscoll would have said "What's the matter with telling me here?" No, it won't do. Driscoll had no business in that direction, anyway. So — there's only one alternative.'

Dr Fell took out a cigar.

`Namely,' he inquired, `that Driscoll went in the same direction as Mrs Bitton did through the arch of the Bloody Tower?'

`Yes. All indications show that. For instance, what Larkin said. She heard Driscoll walk away, and then Mrs Bitton walked up and down in front of the rail a minute or so… to give Driscoll time to go on up there ahead o f her. Driscoll said they mustn't be seen together. Once you get, inside the inner ballium wall, as Larkin said, you're in view of pretty well everybody; especially as it's high ground, and the fog is thin. Larkin had a positive impression that he'd gone on ahead of Mrs Bitton. And that's the reasonable direction for him to have gone, because … '

`Because it's the way to the King's House,' supplied Dr Fell.

`Hadley nodded. `Whatever he had forgotten, and went to do, was in the general's quarters at the King's House. That's the only part of the Tower he ever had any business in… There was somebody he had to speak with on the phone, or some message he had to give Parker. But he never got there.'

`Good work,' said the doctor, approvingly. `By, degrees everything seems to centre round the arch under the Bloody Tower; — Hence we perceive the following points: The arch under this tower is a broad tunnel about twenty feet long,' and the road runs on a steep uphill slant. At the best of times it is rather dark, but on a foggy day it is as black as hell. Why, then, didn't the murderer dump him against the wall and leave him there?'

`Because the body would be discovered too soon. There's too much traffic in that place. So the murderer picked Driscoll up like a ventriloquist's dummy, took a quick look to each side in Water Lane, walked across, and chucked him over the rail on the steps.'

The doctor nodded. He held up one hand and indicated points on his fingers.

`Driscoll walks into the tunnel, then, and meets the murderer. Mrs Bitton waits a short time, and follows, because she doesn't know Driscoll is still in the tunnel. Now do you see what we've got, Hadley? We've got Mrs Bitton at one end of the tunnel, Driscoll and the murderer in the middle and our good friend Mr Arbor at the other end. Haven't we?'

`Every time you begin to elucidate,' said the chief inspector, `the thing gets more tangled up. But that seems clear. Larkin said Mrs Bitton went into the arch at twenty-five minutes to two. Arbor bumped; into her on the other side of it at a coinciding time. Where's the catch?'

'I didn't say there was a catch. Now, following Mrs Bitton at a little distance is the eagle-eyed Larkin, who enters the tunnel next. All this time you must assume the murderer was still in the tunnel with his victim;. otherwise she would have seen him carry the body out. In the tunnel it's very dark and foggy. Mrs Larkin hears somebody moving. That is probably Arbor on his way out from the other side. Thus the tunnel is cleared of traffic. The murderer, who has been crouching there with his victim in a deadly sweat for fear he'll be discovered, carries out the body, throws it over the rail, and escapes., That, I take it, is the summary of events?'

`Yes. That's about it'

Dr Fell squinted down his cigar. `Then,' he said, `where does the enigmatic Mr Arbor fit in? What terrified him?'

Hadley slapped the arm of a chair with his brief-case. `He was passing through that dark tunnel, Fell… and when he was in such a bad state after he left us, the taxidriver said he kept repeating over and over something about a "voice”..’

'Tut, tut,' said the doctor. `Do you think the murderer leaned out and said "Boo!" to him as he passed?'

`I don't expect much from you. But,' the chief inspector said bitterly, `a trifle less heavy humour…. '

But he was not paying a great deal of attention to what Dr Fell said, Rampole noticed.; His eye kept straying to the mantelpiece, to the smashed figure on the hearthstone, and up again to the other image on the shelf. The doctor followed his glance.

'Let me tell you what you're thinking, Hadley,' he observed. `You're thinking: Murderer. Big man; strength. Powerful motive. Man capable of murder, from the emotional depths we saw ourselves. Man with access to crossbow bolt. Man who certainly knew about crossbow bolt. Man so far not even questioned about whereabouts at time of murder, Lester Bitton.'

`Yes,' said Hadley, `I was thinking just that.'

At the door of the flat the bell-buzzer rang. But before Rampole had time to reach the door, it was pushed open…,

'I'm so sorry we're fearfully late!' a girl's voice said, promptly, before, the owner saw anybody. `But it was the chauffeur's night off, and we didn't want to take the big car, and we tried to use the other car, and it got half-way out into the street and stopped. And so we had to use the big car, after all.'

Rampole found himself looking down at a small- face which was poked round the edge of the door. Then by degrees the new-comer' got into the room. She was a plump, very pretty little blonde, with two of the most beaming and expressive blue eyes the American had ever seen; she looked like a breathless doll.

`Er … Miss Bitton?' inquired Rampole.

`I'm Miss Bitton,' she explained, as though she were singling herself out of a group.

Dalrye, thin and blinking, towered over her in the doorway. His sandy hair was disarranged under a hat stuck on the side of his head, and there was a smear of grease under one eye.

Sheila Bitton's large eyes wandered about the room. A shocked look came into them when she saw the broken plaster image.

She looked at Rampole. `You're not… ooh no! I know — you. You're the one who looks like a football-player. Bob described all of you to me. And you're much better looking than I thought you'd be from what he said,' she decided, subjecting him to a peculiarly open and embarrassing scrutiny.

`And I, ma'am,' said Dr Fell, `am the walrus, you see. Mr Dalrye seems to have a flair for vivid description. In what delicate terms, may I ask, did he paint a word-picture of my friend Hadley, here?'

`H'm?' inquired Miss Bitton, arching her brows. She glanced at the doctor, and an expression of delight again animated her sparkling eyes. `Oh, I say! You are a dear!' she cried

Dr Fell jumped violently. There were no inhibitions whatever about Sheila Bitton.

`About Mr Hadley?' she inquired, candidly. `Oh, Bob said he didn't look like anything in particular.'

Dalrye spread out his hands behind her back in helpless pantomime to the others.

`and I've always wanted to meet the police, but the only kind I ever meet are the kind who ask me why I am driving down streets where the arrows point the other way; and why not? because there's no traffic coming and I can go ever so much faster.’ And Then she remembered again why she was here, and stopped with a jerk; the rest of them were afraid there would, be sudden tears.

'Of course, Miss Bitton,' the chief inspector said, hastily. `Now if you'll just sit down a moment and get your breath, then I'm sure.'

`Excuse me,', said Dalrye. `I'm going to wash my hands.' Hee shivered a little, shut his jaws hard and left the room. Miss Bitton said, `Poor Phil' suddenly, and sat down.

There was a silence.

`You….. somebody,' she remarked in a small voice, `somebody's tipped over that pretty little figure on the mantel. I'm sorry, It was one of the things I wanted to take back with me.'

`Had you seen, it before?' asked Hadley. His discomfort had disappeared as he saw a possible lead.

'Why, of course. I was there when they got them.'

'When who got them?'

`At the fair. Phil and Laura and Uncle Lester and I all went to it. Uncle Lester said it was all silly, and didn't want to go, but, Laura used that sort of pitying way she has and he said, "All right, he'd go. He wouldn't ride on any of the swings or giddy-go-rounds or things, though."

`Phil started ragging Uncle Lester, and Uncle Lester got sort of red in the face, but he didn't say anything and then we got to a shooting-gallery where they have the rifles and things, and Uncle Lester spoke up sort of sharp, but not very loud, and said this was a man's game, and not for children, and did Phil want to try? And Phil did, but he wasn't very good. And then Uncle Lester just picked up a pistol instead of a rifle and shot off a whole row of pipes clear across the gallery so fast you couldn't count them; and then he put down the pistol and walked away without saying anything. So Phil didn't like that… I could see he didn't. And every booth we passed he began challenging Uncle Lester to all kinds of games, and Laura joined in too.’

'But about the dolls, Miss Bitton?' Hadley asked.

`Oh yes. It was Laura who won them; they're a pair. It was at throwing darts, and she was ever so good. And, you got prizes for it, and Laura got the highest prize for her score, and she said, "Look, Philip and Mary," and laughed. Because that's what the dolls have written on them, and, you see, Laura's middle name is Mary. Then Uncle Lester said he wouldn't have her keeping that trash; it was disgraceful-looking and of course I wanted them ever so badly. But Laura said no, she'd give them to Philip if Mary couldn't have them. And Phil did the meanest thing I ever knew, because he made the absurdest bow and said he would keep them.

`All the way back I kept teasing Phil to give them to me; and he made all sorts of ridiculous speeches that didn't mean anything, and looked at Laura, but he wouldn't give them to me. And that's how I remember them, because they remind me of Phil… You see, I even asked Bob to, see if he could get Phil to give them to me; I asked him the next day.. that was ages ago… when I called Bob on the telephone, because I always make him ring me up every day, or else I ring him up.'

She paused, her thin eyebrows raised again as she saw Hadley's face.

`You say,' the chief inspector observed, in a voice he tried to make' casual, `that you talk every day to Mr Dalrye on the telephone?'

Rampole started. He remembered now. Earlier in the evening Hadley had made a wild shot when he was building up a fake case against Laura Bitton in front of her husband. He had said that Dalrye had informed Sheila of Driscoll's proposed visit to the Tower at one o'clock, because Dalrye talked to her on the telephone that morning; and that, therefore anybody in the Bitton house could have known of the one-o'clock engagement. Hadley, thought it was a wild shot, and nothing more. But, Rampole remembered, Lester Bitton had shown no disposition to doubt it.

Sheila Bitton's blue eyes were fixed on Hadley.

`Oh, please!' she said, `don't you preach! You sound like Daddy. He tells me what a fool I am, calling up every day, and I don't think he likes Bob, anyway, because Bob hasn't any money.'

`My, dear Miss Bitton,' Hadley interposed, with a sort of desperate joviality, `I certainly am not preaching. I think it's' a splendid idea.'

`You're a dear!' cooed Miss Bitton. `And they rag me so about it, and even Phil used to phone me and pretend he was Bob and ask me to go to the police station because Bob had been arrested for flirting with women in Hyde Park, and was in gaol, and would I bail him out, and '

`Ha, ha,' said Hadley. `But what I wanted to ask you, did you speak to Mr Dalrye to-day?'

`Yes, I- did talk to him to-day.'

`When, Miss Bitton? In the morning?'

`Yes. That's when I usually call, you know, because then General Mason isn't there.'

`But, `Miss Bitton, when you spoke to Mr Dalrye this morning did he tell you that Philip Driscoll… your cousin, you know… was coming to see him at the Tower?'

`Yes,' she said, after a pause. `I know, because Bob wanted to know what sort of mess Phil had got into now, and did I know anything about it? He told me not to say anything about it to the others'

`And you didn't?'

`I sort of hinted, that's all, at the breakfast table. 1 asked them if they knew why Phil was going to the Tower of London at one o'clock, and they didn't know, and of course I obeyed Bob and didn't say anything more….'

`I fancy that should be sufficient,' said Hadley. `Was any comment made?'

`Comment?' the girl repeated, doubtfully. `N — no; they just talked a bit, and joked.'

`Who was at the table?'

`Just Daddy, and Uncle Lester and that horrible man who's been stopping with us; the one who rushed out this afternoon without saying a word to anybody.'

`Was Mrs Bitton at the table?'

`Laura? Oh! Oh no. She, didn't come down. She wasn't feeling well, and, anyway, I don't blame her, because she and Uncle Lester must have been up all last night, talking; I heard them, and. ’

`But surely Miss. Bitton, something must have been said at the breakfast table?'

`No, Mr Hadley. Truly. Of course I don't like being at the table when just Daddy and that horrible Mr Arbor are there, because mostly.I can't understand what they're talking about, books and things like that, and jokes I don't think funny. Or else the talk gets horrid, like the night when Phil told Uncle Lester he wanted to die in a top-hat. But I there wasn't anything important that I heard. Of course, Uncle Lester did say he was going to see Phil to-day…. But there wasn't anything important. Really.'