become very mysterious and private and talk enigmatically—is that the word?—about dentists and swimming and the 'Plough and Horses,' and—well, what was it all about? You simply vanished out of sight; I didn't know what on earth we were talking about."
Antony laughed and apologized.
"Sorry, Bill. I felt like that suddenly. Just for the last half-hour; just to end up with. I'll tell you everything now. Not that there's anything to tell, really. It seems so easy when you know it—so obvious. About Mr. Cartwright of Wimpole Street. Of course he was just to identify the body."
"But whatever made you think of a dentist for that?"
"Who could do it better? Could you have done it? How could you? You'd never gone bathing with Mark; you'd never seen him stripped. He didn't swim. Could his doctor do it? Not unless he'd had some particular operation, and perhaps not then. But his dentists could—at any time, always—if he had been to his dentist fairly often. Hence Mr. Cartwright of Wimpole Street."
Bill nodded thoughtfully and went back again to the letter.
"I see. And you told Cayley that you were telegraphing to Cartwright to identify the body?"
"Yes. And then of course it was all up for him. Once we knew that Robert was Mark we knew everything."
