‘Do you mean to say she charged about the place with this thing hung round her neck!’ Fox exclaimed. ‘It must be worth a fortune. And it’s uncommonly pretty,’ he added. ‘Uncommonly so.’

‘That, unless we’re on the wrong track altogether, is what the Jampot thought. Go ahead, you two. Dabs and pictures.’

They were about to leave the room when the telephone rang. Tillottson answered it. ‘You’d better report to Mr Alleyn,’ he said. ‘Hold on.’ He held out the receiver. ‘PM result,’ he said.

Alleyn listened. ‘Thank you,’ he said. ‘What we expected.’ He hung up. ‘She didn’t drown, Fox. Pressure on the carotids and vagus nerve. The mixture as before and straight from the Jampot. All right, Bert. Show us your captives.’

They were in the little charge-room, lounging back on a couple of office chairs and chewing gum. They were as Natouche had described them and their behaviour was completely predictable: the quarter sneer, the drooped eyelid, the hunched shoulder and the perpetual complacent chew. The girl, Alleyn thought, looking at her hands, was frightened: the man hid his hands in his pockets and betrayed nothing but his own insolence.

‘They’ve been charged,’ Tillottson said, ‘with theft. They won’t make a statement.’

Alleyn said to the young man: ‘I’m going to put questions to you. You’ve been taken into custody and found to be in possession of a jewel belonging to a lady into whose death we are inquiring. Driving licence?’ He looked at Tillotson who slightly nodded. The young man, sketching boredom and impertinence in equal parts, raised his eyebrows, dipped his fingers into a pocket and threw a licence on the table. He opened his mouth, accelerated his chewing and resumed his former pose.

The licence was made out in the name of Albert Bernard Smith and seemed to be in order. It gave an address in Soho.

‘This will be checked. The night before last,’ Alleyn said, ‘you were on the tow-path at Crossdyke alongside the Zodiac wearing those boots. You had parked your bicycle under a hedge on the left-hand side of the road above the lock. Later that night you were here at Ramsdyke. You arrived here, with a passenger. Not:’ he looked at the girl, ‘this lady. You carried your passenger—a dead weight—’ For two seconds the slightly prognathic jaw noticed by Dr Natouche, stopped champing. The girl suddenly re-crossed her legs.

‘—a dead weight,’ Alleyn repeated, ‘down to the weir. Her pyjamas caught on a briar. You did what you’d been instructed to do and then picked up your present companion and made off for Carlisle where you arrived yesterday in time to send a telegram to the Skipper of the Zodiac. It was signed Hay Rickerby-Carrick which is not much like Albert Bernard Smith. Having executed this commission you turned south and were picked up by the police at Pontefract.’