Remember Benjen Stark, Ned's younger brother who was a ranger in the Night's Watch?
It was Benjen's disappearance and the appearance of the wights that led Mormont to take the Night's Watch north of the Wall to investigate. Which then led to Jon meeting Ygritte and the wildlings.
Book readers have long held the theory that Benjen is Coldhands – an undead, hooded character we haven't seen in the show yet. However, a note between George R. R. Martin and an editor on the manuscript for A Dance with Dragons seems to discredit that theory.
But show fans are now getting hype thanks to Joseph Mawle, the actor who plays Benjen, appearing in the cast list on IMDb for Season 6, Episode 6 as the "Brother Beyond the Wall".
But Imgur user KainoaBorges has pieced together Meera and Bran's scenes from the Episode 6 preview with a scene in the Season 6 trailer to suggest a hooded figure is going to save them from the wights – a hooded figure who might just be Benjen Stark.