Robert Cairn looked out across the quadrangle. The moon had just arisen, and it softened the beauty of the old college buildings, mellowed the harshness of time, casting shadow pools beneath the cloisteresque arches to the west and setting out the ivy in stronger relief upon the ancient walls. The barred shadow on the lichened stones beyond the elm was cast by the hidden gate; and straight ahead, where, between a quaint chimney-stack and a bartizan, a triangular patch of blue showed like spangled velvet, lay the Thames. It was from there the cooling breeze came.

But Cairn’s gaze was set upon a window almost directly ahead, and west below the chimneys. Within the room to which it belonged a lambent light played.

Cairn turned to his companion, a ruddy and athletic looking man, somewhat bovine in type, who at the moment was busily tracing out sections on a human skull and checking his calculations from Ross’s Diseases of the Nervous System.

‘Sime, ‘ he said, ‘what does Ferrara always have a fire in his rooms for at this time of the year?’

Sime glanced up irritably at the speaker. Cairn was a tall, thin Scotsman, clean-shaven, square jawed, and with the crisp light hair and grey eyes which often bespeak unusual virility.

‘Aren’t you going to do any work?’ he inquired pathetically. ‘I thought you’d come to give me a hand with my basal ganglia. I shall go down on that; and there you’ve been stuck staring out of the window!’

‘Wilson, in the end house, has got a most unusual brain, ‘ said Cairn, with apparent irrelevance.

‘Has he!’ snapped Sime.

‘Yes, in a bottle. His governor is at Bart’s; he sent it up yesterday. You ought to see it.’

‘Nobody will ever want to put your brain in a bottle, ‘ predicted the scowling Sime, and resumed his studies.

Cairn relighted his pipe, staring across the quadrangle again. Then—

‘You’ve never been in Ferrara’s rooms, have you?’ he inquired.