The Professor cut him off impatiently. "I'm disappointed in John Smithers," he thought. "He has no stamina. A man of low birth, evidently. A mere mountain of muscle. I know the species."

For a while he paced the room. Then he rang the bell, but this time there was no coherent response. The gasps sounded like, "Sit on her head, Blyth—keep her down, man. Whoa, mare!—mind that fencing—snow again—what ho! she bumps—all down the road and round the corner——"

"For heaven's sake, keep cool, Smithers," cried the Professor. "I want some more observations. Don't lose your head yet. You've all the night in front of you."

"Squadron, right wheel! Draw swords! Charge! Down with 'em! Boers, Japs, and Russians. Get home, lads! Give it 'em hot! Hurrah! I've killed a sergeant-major." Then indistinct mumbling and cackling laughter came through the telephone.

The Professor was disturbed. The end had come sooner than he had expected, for John Smithers had only been there an hour and a half, and he had calculated on a much longer time. But the symptoms were, on the whole, what he had expected. Green hands, though. What if the extremities were blue after all, and Cantrip right?

He rang the bell. There was no response. Once more, and yet again. Still there was silence.

The Professor hung up the receiver gloomily. "I'm afraid I shall have to go to him. He's unconscious, and continued exposure might be serious."

He went down the corridor, pulled back the bolts, and opened the door. The room was in absolute darkness. The Professor was intensely surprised. "What on earth has he done with the radium?" he thought. "Good heavens! Surely he hasn't really swallowed it!"

He stepped carefully across the threshold towards the electric pendant in the centre of the room. He started. The door had closed behind him with a loud click. He switched on the light, and peered round the floor for John Smithers. He was alone. Neither Smithers nor the radium was there!

At that moment the telephone rang.