In an AU where a small number of the population become Changelings at a young age, at 17 John Watson believes he's destined for Normal life but then the Change takes him and he is sent to the Baker Institute. There he meets Sherlock Holmes. John/Sherlock

"What if I died tomorrow?" Sherlock turned back to the computer with a sigh. "I hardly see how my opinion matters. My belief or disbelief in your soul certainly won't determine whether or not it exists." Not a character death, just some introspection.

Mummy has arranged Mycroft's marriage with an ex-army doctor. However, John meets Sherlock first, and sparks fly.