Sherlock's investigation reveals that while Moriarty is not involved in the attempt on his father's life, her organization definitely is. Krasnov, the man who shot Morland and killed his girlfriend Sabine, explodes a bomb in Morland's office after killing two people.
After further investigation, Sherlock discovers the new face of Moriarty's organization, a brilliant, well-educated economics professor named Joshua Vikner. Vikner readily acknowledges this; he is the father of Moriarty's daughter and states that both Sherlock and Joan are off-limits, per Moriarty's orders.
Morland pays Sherlock a visit and declares that Sabine's blood is on Sherlock's hands, because Sherlock did not follow through after Moriarty's arrest several years before on the assumption that her organization would simply collapse without her.
The NYPD captures Krasnov, who is defiant an uncooperative, as much of their evidence remains circumstantial.
Sherlock meets with Vikner again; Vikner requests Sherlock broker a truce between his organization and Morland. Sherlock informs him that Morland wants his head and won't settle for anything less. Vikner warns Sherlock that this means war.
The team finds evidence to link Krasnov to the bomb. As Krasnov is being brought to make a deal, however, a subverted cop murders him before committing suicide.
Sherlock and Joan return to the brownstone and find a large bomb waiting for them.