John misses dangers and that adrenaline rush and Sherlock needs to win John's friendship back so Mary plans a kidnapping of John to speed things up before the wedding. Sherlock figures this out. What does he tell John. Is this dangerously playing with their lives or is it the ultimate gift?
(Was thinking of this as a variation of a deleted scene from Private Life of Sherlock Holmes where Watson tries to create a mystery so Holmes isn't bored.)