Watson and Holmes are returning from the lock-and-key shop where they've ordered an extra apartment key because Watson lost his.
As they arrive, Watson bounds up the steps to 221B Baker Street and barges into their apartment as Sherlock Holmes follows him.
"I'll show you my deductions today Holmes!", he says. "I can deduce too!"
Sherlock Holmes shows him the only key to the apartment and says, "What can you ded...