Ben Foster was the brother of Hayden Foster.
Ben and his mother were unaware of his sister's relationship with Justin. Ben found out only after a friend of Hayden - who didn't like Justin - chose to inform Ben about him. When Ben came to pick Hayden up from work, Hayden lied about having a boyfriend and tried to sneak away to return to Justin.
A disguised figure attacked Hayden while she was on her way, leaving her unconscious. Ben soon stumbled upon the scene and the figure proceeded to attack and kill Ben by ripping his heart out.
Ben's death drew in the attention of three hunters: Sam and Dean Winchester and Claire Novak. The trio interviewed both Justin and Justin's co-worker Connor, but came to suspect Connor. Due to an infectious bite, Hayden began transforming into a werewolf. British Men of Letters Mick Davies killed her as a result.
Justin, who was not only the assailant but also a werewolf, had intended to turn Hayden into his mate. Her death drove him to kidnap Claire instead. This led Sam, Dean and Mick to arrive at his home. Justin was subsequently killed by Mick.