Sherlock and Joan walk into the brownstone to find a bomb of the same type they had previously encountered, linked to Joshua Vikner. Sherlock swiftly disarms it and deduces that someone was setting Vikner up.
Morland's head of security, Mr. Gray, is seriously injured by the would-be bomber, who is killed. They link the bomber to a woman from the Iranian mission.
Zoya Hashemi informs them that they grossly underestimated the breadth of Moriarty's network, and they cannot rely on Moriarty's protection on Sherlock and Joan to hold out. Hashemi informs them that Vikner was one of two possible options for Moriarty's "throne," the other being an unconnected outside, new blood: Morland Holmes himself.
Sherlock and Joan decide to frame Vikner for murder to flush him out. Unfortunately, Vikner vanishes before the FBI can arrest him.
Morland throws in with Zoya Hashemi to take down Vikner, and he informs Sherlock that he is taking over Moriarty's organization with the specific intention of keeping Sherlock safe -- and dismantling the vast criminal network from the inside.
He departs from New York, but not before gifting Sherlock with one of his more valuable New York properties, which Sherlock decides to sell after some consultation with Joan.