Father, Son, or Both
Assign the Reigate crime's parts — the pen, the pistol, the panic — to the right Cunningham.
The note proves two authors; the night held one shot and one struggle in a dressing-room. Weigh each element against each squire, then read the canon's division of guilt.
Drawn from The Reigate Squires (The Memoirs of Sherlock Holmes, 1893) — read the summary & analysis, or try The Torn Corner of Paper, this story's game. More at the Game Room and the tool bench.