'I had a think about it when I got home,' went on the undertaker. 'And I believe there's a chap who might give you some more on it. He came to one of our meetings too. Last year. Gave us a talk on the Black Death. His name is Kinlock, Dr Christopher Kinlock. He's a medical historian. He lives somewhere in the docks area - the bit they've all smartened up. You should be able to find him all right.'
Dr Kinlock himself answered the door. There was an oddly shaped knocker. 'This house,' he said, 'was used by an apothecary two hundred years ago. I'm very pleased to have it now.' He indicated the curved steel knocker. 'That,' he said proudly, 'is a third-generation artificial hip, a prosthesis; makes a wonderful bit of door furniture, don't you think?'
Davies said uncertainly that he did. The doctor led the way through a panelled hall, beyond glass doors into a room where a gas fire was burning boldly.
Around the walls were showcases containing items of human anatomy. Davies could see a library through another door with an encased skeleton grinning at nothing. There were other skulls, bones and nameless things in jars. The death mask of a bald man occupied another container. 'Unusual room,' mentioned Davies, accepting the doctor's Scotch.
'An unusual facet of Dockland development,' smiled Kinlock. 'It's not all fancy former warehouses.' He was a small Scot with ginger eyebrows. 'It's been a fine opportunity to gather interesting specimens from medical history. I'm adding to it all the time. The death mask is of Mikhail Bakunin, the father of modern anarchy, one of only twelve made. One day, I would love to buy Napoleon's testicle.'
'That,' agreed Davies vaguely, 'would be worth having.'
'Now, you had a little poser for me,' said Kinlock. 'Not much of one because, even from your telephone conversation, I think I know what we are talking about.'
These,' said Davies. He had taken a further two screws from Lofty's box and reclaimed the first from Walter Pitt. He held the three wooden screws out in the palm of his hand.
Kinlock picked up one with a musing smile. 'Cunningly made, aren't they,' he said. 'You'd have a job having something like this turned today. They needed to be the hardest wood, and of course, non-toxic'
'What,' asked Davies, 'were they for?'
'Orthopaedic,' said Kinlock brightly. 'Screwing together bones.' He twisted one of the screws as he turned and led the way into the further room. From a shelf he eased a heavy red book and, perching a pair of rough glasses on the ridge of his nose, turned the big pages. 'Developed,' he paraphrased, 'in the nineteen twenties. A revolution in orthopaedic surgery.' Once more he twirled the wooden spiral. 'Cunning,' he said again.
Davies asked cautiously, 'How ... common were they, at the time?'
'Not so very. It wasn't long before a stainless steel screw was developed, obviously an advantage because this little lady was very finicky and very costly to make.' He looked quizzically at Davies. 'I have, incidentally, only a very vague idea why the Metropolitan Police should want to know. Is it very secret?'