Julian Duval is a werewolf, brother to Violet Duval and belongs to one of the five monster families that run Chicago. Julian may or may not have been involved with the death of Irv Sokolowski's young son, along with Sal Lassiter.
At the monster club in the backroom of upscale restaurant Il Secundo, Julian Duval tells the recently arrived Sal Lassiter to leave the club, when Sal refuses Julian punches Sal, they tussle with each other, and as Sal gets the upper hand Julian starts to turn into a werewolf, and they are quickly separated. As Julian leaves the bar, the lights suddenly go out and a clawed hooded figure appears and begins slashing at any monsters that get in his way, including Sal, ultimately killing him.
After the attack at the club, Julian is seen meeting with a member of the djinn family about whether the Lassiter's will make a move on him as they believe he was behind the death of Sal. When Violet attempts to question him about Sal's death, he tells her Margo Lassiter thinks he killed Sal and wants him dead, and he won't say anything different, as he wants war to erupt between the shapeshifters and werewolves.