this girl everyone thought was sophie's body double is actually alys karstark! in the books, alys has dark brown hair, but in the show they made her a redhead. alys is the daughter of rickard karstark, a traitor to house stark.
in the books, she seeks jon's help at castle black because she is fleeing from her uncles and cousins who conspire to marry her to inherit her inheritance and karhold castle, home to the karstark house. to avoid this, jon arranges for melisandre to marry alys to sigorn, magnar of thenn.
in the show, harald karstark,alys brother, allied himself with ramsay and his fate at the end of the season was uncertain: it is unknown whether harald was killed in battle captured by jon or fled. we also don't know what the degree of kinship between alys and harald in the tv series will be.
theories that she will be jon's bethroted in the show, or that something will happen with her in sansa's place. most likely, alys will have to swear allegiance to jon, which means she will spend some time in winterfell, where sansa is. and while there, someone will try to kill sansa while jon is in the south, and will confuse both killing alys in sansa's place.
what do you think?