Joan rushes back to New York after Captain Gregson is shot. She wants to help with the investigation. She tells Marcus that since Sherlock can't return to the States because of a murder charge, he will help from London. But he actually has snuck back in and is staying at their brownstone. Marcus pushes back his Marshall training. Joan goes to visit Gregson while Sherlock searches for the crime scene. Sherlock determines Gregson hadn't been coming from the station. Soil on Gregson's clothing leads them to a baseball field, where he was shot. Sherlock removes a panel from the dugout and finds a corpse. The body was Tim Bledsoe, reported missing eight months earlier. He was shot with the same caliber bullet as Gregson. Tim's mother had contacted Gregson, which is how he'd gotten involved. She suspected her ex-husband Marty, a cop. Marty had alibis for both shootings, but gave Marcus others with beefs against Tim. Joan urges Sherlock to go see the fading Gregson. Marcus suspects Tim's friend Dylan Halleran, who has a violent history and is wanted for skipping bail. But the last time Dylan had seen Tim was when Tim stole his car. Checking out the contents of the trunk, Sherlock decides Tim was planning to bomb the Bridgeport Ferry. Tim's mother admits there were some strange charges on her credit card the week Tim disappeared. Paige overhears some of Sherlock's talk to Gregson. Joan finds surveillance of Tim being abducted, by Patrick Meers, who said Tim had attacked him. Meers hears the cops coming, and Marcus has to talk him into surrendering. Meers admits to shooting Tim and Gregson but denies having anything to do with TIm's planned bombing. Sherlock urges Joan to investigate a possible terror cell with Marcus. Then he surrenders to the FBI.