A shadow man that reduces people to ashes serves as the frame in which Agent Broyles reveals his own past, contrary to the most popular belief it wasn't the love affair with Massive Dynamci's Nina Sharp what caused the end of his marriage but rather his own marriage to Fringe Division illustrated in the first scene where a little boy plays with him until the latest call makes him flee from his dinner table like he probably did back when he still had a family.
The contrast with the Bishop household starts early in the episode as Walter remembers some particularly embarrasing moments of Peter's childhood and continue all the way up to the scene where Walter is caught up in a music aria solving a formula as Peter & Astrid watch him in awe, a formula that links all the way back to Russian technology and their work on Fringe science.
As Walter involves and expands his own family, Broyles alienates the only family he has left, Olivia practically has to force him to confess who was his contact, the brother of a Russian cosmonaut called Alex Vasiliev whose shado is probably still killing people as he lies on a coma he hasn't wake up from since Broyles's first case. By the time they contain the shadow both the brother as well as a few others have already been killed.
In the end Broyles finally goes home to share the news with his ex-wife even if he can no longer share his life with her.