Sherlock enlists the help of The Doctor after his ‘death’ to ensure they vanquish every possible strand of Moriarty’s criminal web. While traveling through time and sabotaging the villain’s development, Sherlock inadvertently comes across a young John Watson.
After a series of unfortunate events reveal that his future-friend is living in an abusive home, Sherlock makes a rash ‘sentimental’ decision… and takes John away with him.
The Doctor warns Sherlock about his actions (and the repercussions that could come with it) and insists he give John up once they’ve gotten him to a safer, more stable location.
To avoid arousing suspicion along the way, Sherlock dies his hair blonde and passes John off as his ‘son’ while they travel. He remains incredibly protective and oddly endearing as he helps the frightened child slowly find his confidence, and trust again.