A young Mycroft brings his girlfriend home from university to introduce to Mummy. Unfortunately, this means she has to meet Sherlock as well.

"Sometimes the only reason you don't let go of something that makes you sad is because it was the only thing that made you happy. Sometimes I get sad, John. And when I do, I completely shut down. I stare blankly at the wall and it doesn't matter what they say. Because in that moment, I don't exist. I'm drowning John and they're watching me, screaming 'learn to swim'."

John finds Sherlock three years after he thought he'd buried him, scared and injured; broken to such an extent he can barely recognise those trying to help him. Battling against too many unanswered questions and his own feelings, John sets out to put him back together, but never stops to consider Sherlock's return may be part of a greater punishment in store for the both of them.

Sherlock and John are finally in a relationship. Then, Sherlock's ex-lover shows up one day at his Baker Street flat, saying that he is ready to try again. However, there's more to their past relationship than meets the eye. Will Sherlock tell John why this man has so much control over him? Will John be able to figure it out in time to save Sherlock from the demons of his past?

Greg Lestrade is being held to ransom in a cellar with Sherlock and his brother, who seems to like umbrellas an awful lot. Who'll arrive to save them first? Scotland Yard, the government, or John Watson?