Margo Lassiter is David's sister and the head of the Shapeshifter family. She becomes the head of the family in the wake of a tragedy. She is in her 20s.
Margo places a call to her younger brother David to inform him of Sal's death. As Freddie Costa reports to Margo the concerns the other monster families have over who is going to run things after the death of Sal. Margo tells Freddie to tell the other families that she will be running things from now on, whether they like it or not.
When David arrives at the Lassiter residence, he questions Margo about what happened to Sal. Margo tells him that Sal was killed by Julian Duval, and that she has plans to go to war with the werewolves. As David tries to question if Julian was involved, Margo tells him that he wanted to live as a human and this is none of his business.
After David brings proof that clears the Duvals in the murder of Sal, he states his intention to return to the family, for which Margo welcomes him home with hug, however her demeanor turns cold while she hugs her brother.
Margo was described as professional, strong-willed, determined, ambitious and as an ex-punk rocker gone corporate.