Episode 1: Many Happy Returns (Dec/24/2013)
After Sherlock's passing two years ago, someone still isn't quite convinced that he is dead.
Episode 2: The Empty Hearse (Jan/01/2014)
Two years after his "death," Sherlock returns to London and discovers that John has moved on. However, he soon needs his friend's help when he helps his brother Mycroft investigate an underground terrorist network planning an attack somewhere in London.
Episode 3: The Sign Of Three (Jan/05/2014)
Sherlock tries to get through making the best man's speech at John and Mary's wedding. However, his mind soon turns to other matters... like the fact that one of the guests is a killer's target.
Source: TVRage