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.