Then suddenly, beneath the disguise of the mess, he saw the clue. A footmark! No less. A crimson footmark on the gray concrete! Riglett, who had been waiting patiently two yards away, now coughed plaintively. The sound recalled Mr. Downing to mundane matters. "Get your bicycle, Riglett," he said, "and be careful where you tread. Somebody has upset a pot of paint on the floor." Riglett, walking delicately through dry places, extracted his bicycle from the rack, and presently departed to gladden the heart of his aunt, leaving Mr. Downing, his brain fizzing with the enthusiasm of the detective, to lock the door and resume his perambulation of the cricket field. Give Doctor Watson a fair start, and he is a demon at the game. Mr. Downing's brain was now working with a rapidity and clearness which a professional sleuth might have envied. Paint. Red paint. Obviously the same paint with which Sammy had been decorated. A footmark. Whose footmark? Plainly that of the criminal who had done the deed of decoration. Yoicks! There were two things, however, to be considered. Your careful detective must consider everything. In the first place, the paint might have been upset by the groundsman. It was the groundsman's paint. He had been giving a fresh coating to the woodwork in front of the pavilion scoring box at the conclusion of yesterday's match. (A labor of love which was the direct outcome of the enthusiasm for work which Adair had instilled into him.) In that case the footmark might be his. _Note one_: Interview the groundsman on this point. In the second place Adair might have upset the tin and trodden in its contents when he went to get his bicycle in order to fetch the doctor for the suffering MacPhee. This was the more probable of the two contingencies, for it would have been dark in the shed when Adair went into it. _Note two_: Interview Adair as to whether he found, on returning to the house, that there was paint on his shoes. Things were moving. * * * * * He resolved to take Adair first. He could get the groundsman's address from him. Passing by the trees under whose shade Mike and Psmith and Dunster had watched the match on the previous day, he came upon the Head of his house in a deck chair reading a book. A summer Sunday afternoon is the time for reading in deck chairs. "Oh, Adair," he said. "No, don't get up. I merely wished to ask you if you found any paint on your shoes when you returned to the house last night." "Paint, sir?" Adair was plainly puzzled. His book had been interesting, and had driven the Sammy incident out of his head. "I see somebody has spilled some paint on the floor of the bicycle shed. You did not do that, I suppose, when you went to fetch your bicycle?" "No, sir." "It is spilled all over the floor. I wondered whether you had happened to tread in it. But you say you found no paint on your shoes this morning?"