Billy has decided the Angels of Death killed Jason and that the answer is to take their clubhouse apart, and he has a Pegorino capo sitting in the Lost's own bar while he decides it. The ride out is another of his impromptu races; the arrival is a grenade launcher through an upstairs window.
What the chapter finds in the basement is worth more than the building: a heroin stash Billy tells them is two million dollars' worth. He is lying about whose it is, and the rest of the episode is the bill for that lie arriving in instalments.