Sherlock Holmes and Dr. Watson find themselves in a university town when a tutor and lecturer of St Luke's College, Mr. Hilton Soames, brings him an interesting problem.
Soames had been reviewing the galley proofs of an exam he was going to give when he left his office for an hour.
When he returned, he found that his servant, Bannister, had entered the room but accidentally left his key in the lock when he left, and someone had disturbed the exam papers on his desk and left traces that show it had been partially copied.
Bannister is devastated and collapses on a chair, but swears that he did not touch the papers.
Soames found other clues in his office: pencil shavings, a broken pencil lead, a fresh cut in his desk surface, and a small blob of black clay speckled with sawdust.

Soames wants to uncover the cheater and prevent him from taking the exam, since it is for a sizeable scholarship.
Three students who will take the exam live above him in the same building.
The first, Gilchrist, is athletic, being a hurdler and a long-jumper, and industrious (in contrast to his father who squandered his fortune in horse racing); the second, Daulat Ras, is described as quiet and methodical; the third is Miles McLaren, a gifted man but thoroughly dissolute and given to gambling.

Holmes examines the office.
The cheater obviously took the papers over to the window one by one while he copied them so that he could see Soames returning, but as it happens, Soames did not come back the usual way.
A nearby door leads to Soames's bedroom.
Upon examining that, Holmes finds another, similar, sawdust-speckled blob of clay.
He stuns Soames by telling him that the cheater, upon hearing his approach, hid in Soames's bedroom.
He was there, hiding behind a curtain, all the time that Soames was questioning Bannister.

The next morning, Holmes and Watson return to Soames's office.
Holmes confronts Bannister who he believes is not telling all he knows.
Bannister will not own up to anything, and insists that there was no-one in Soames's office while he was there.
Holmes, however, sends for Gilchrist, and proceeds to lay out his results.

 The cheater was someone who knew the exam proofs were there.
This could only be Gilchrist because the proofs' whereabouts had been kept secret, and Gilchrist was the only one tall enough to look in through Soames's window to see his desk.
Holmes has also identified the blobs as the special clay found in the long-jump pit, further implicating Gilchrist.
Gilchrist reveals his guilt by reproaching Bannister for his apparent treachery.
Bannister was indeed the one who covered for Gilchrist.
He felt that he had to, for old times' sake: Bannister was once Gilchrist's father's butler.

Holmes then explains the remaining clues.
The scratch on the desk was caused by Gilchrist's spiked jumping shoes as he grabbed them in his haste, and the clay blobs fell from his shoes.
Bannister had collapsed in the chair to hide Gilchrist's gloves, which he saw had been left on the chair.
For his part, Gilchrist credits Bannister with convincing him not to profit from his misdeed, and presents Soames with a letter stating his wish not to sit the exam, but accept an offer in South Africa for the Rhodesian Police.
Sherlock Holmes and Dr. Watson find themselves in a university town when a tutor and lecturer of St Luke's College, Mr. Hilton Soames, brings him an interesting problem. Soames had been reviewing the galley proofs of an exam he was going to give when he left his office for an hour. When he returned, he found that his servant, Bannister, had entered the room but accidentally left his key in the lock when he left, and someone had disturbed the exam papers on his desk and left traces that show it had been partially copied. Bannister is devastated and collapses on a chair, but swears that he did not touch the papers. Soames found other clues in his office: pencil shavings, a broken pencil lead, a fresh cut in his desk surface, and a small blob of black clay speckled with sawdust.
Soames wants to uncover the cheater and prevent him from taking the exam, since it is for a sizeable scholarship. Three students who will take the exam live above him in the same building. The first, Gilchrist, is athletic, being a hurdler and a long-jumper, and industrious (in contrast to his father who squandered his fortune in horse racing); the second, Daulat Ras, is described as quiet and methodical; the third is Miles McLaren, a gifted man but thoroughly dissolute and given to gambling.
Holmes examines the office. The cheater obviously took the papers over to the window one by one while he copied them so that he could see Soames returning, but as it happens, Soames did not come back the usual way. A nearby door leads to Soames's bedroom. Upon examining that, Holmes finds another, similar, sawdust-speckled blob of clay. He stuns Soames by telling him that the cheater, upon hearing his approach, hid in Soames's bedroom. He was there, hiding behind a curtain, all the time that Soames was questioning Bannister.
The next morning, Holmes and Watson return to Soames's office. Holmes confronts Bannister who he believes is not telling all he knows. Bannister will not own up to anything, and insists that there was no-one in Soames's office while he was there. Holmes, however, sends for Gilchrist, and proceeds to lay out his results.
 The cheater was someone who knew the exam proofs were there. This could only be Gilchrist because the proofs' whereabouts had been kept secret, and Gilchrist was the only one tall enough to look in through Soames's window to see his desk. Holmes has also identified the blobs as the special clay found in the long-jump pit, further implicating Gilchrist. Gilchrist reveals his guilt by reproaching Bannister for his apparent treachery. Bannister was indeed the one who covered for Gilchrist. He felt that he had to, for old times' sake: Bannister was once Gilchrist's father's butler.
Holmes then explains the remaining clues. The scratch on the desk was caused by Gilchrist's spiked jumping shoes as he grabbed them in his haste, and the clay blobs fell from his shoes. Bannister had collapsed in the chair to hide Gilchrist's gloves, which he saw had been left on the chair. For his part, Gilchrist credits Bannister with convincing him not to profit from his misdeed, and presents Soames with a letter stating his wish not to sit the exam, but accept an offer in South Africa for the Rhodesian Police.
The Adventure of the Three Students