Ha! it is commencing.
Look at his thumb--that is the danger signal!" Colwyn looked across the room again.

The young man was still sitting in the same posture, with his gaze bent on the open sea.

His left hand was extended rigidly on the table in front of him, with the thumb, extended at right angles, oscillating rapidly in a peculiar manner.
"This attack may pass away like the other, but if he looks round at anybody, and makes the slightest move, we must secure him immediately," said Colwyn's companion, speaking in a whisper.
He had barely finished speaking when the young man turned his head from the open window and fixed his blue eyes vacantly on the table nearest him, where an elderly clergyman, a golfing friend, and their wives, were breakfasting together.

With a swift movement the young man got up, and started to walk towards this table.
Colwyn, who was watching every movement of the young man closely, could not determine, then or afterwards, whether he meditated an attack on the occupants of the next table, or merely intended to leave the breakfast room.

The clergyman's table was directly in front of the alcove and in a line with the pair of swinging glass doors which were the only exit from the breakfast-room.