Frank hangs up his phone and tells John about the shoe print results. John thinks the shoe print clue is too easy, and Frank agrees that Pesco is toying with them. John shows Frank the rebreather they found in the sewer. John explains that the mouthpiece has a one-way valve, so he's going to try to isolate Pesco's saliva residue. Frank realizes that would give them a DNA sample, which would give them Pesco's real identity. Assuming he's in the database. And then what does that get them? Are they assuming that he used his real name to rent or lease his warehouse? It's best not to think about these things too hard. John pulls a sample from the valve and spreads it on a slide. When he looks under the microscope, there's no genetic material. Frank asks if the sewer water washed it away. John says that's not possible. Frank says he might have dry mouth. Of course, they don't know for sure that Pesco actually used it, right? John realizes that Pesco doesn't have any saliva, which is a rare condition. John races to the computer and looks up medications used to treat that rare condition, and then finds out who in the area has a prescription for that medication. John realizes that one of the names is Theresa Avila, which stands for St. Theresa of Avila, the patron saint of chess. John grabs the address, but thinks it's still too easy.
The cop cars and SWAT teams roar up to the address Stella got. Frank calls Ruiz and warns him that he's walking into a trap. Ruiz wants more evidence. The SWAT team breaks down the warehouse door and starts to enter. Frank urges them to pull back, just as the SWAT team enters and a bomb goes off. Cut to Pesco, watching the whole thing on his monitors. Frank hangs up and tells John they are on their own, and they have fifteen minutes at the most.
Frank and John arrive at their address. Frank hands John a gun. John points out that he's not licensed to carry a weapon. Frank says that John is a fugitive, so an unlicensed weapon is the least of his worries. Frank adds that they should take Pesco if they can. John says that if Pesco decides to take Lt. Bosslady out with him, they go to Plan B. As they prepare to enter, John asks Frank to give him thirty seconds. Frank says that he's taking the shot if he gets it. Frank open the door, makes sure it's clear, and then nods John in. Pesco watches John enter on his monitor. He hears John yelling to him, saying that Pesco wants someone to stop him, and that's why John is there. John bursts into the room, brandishing his gun. He tells Pesco that the game is over. Pesco takes refuge behind Lt. Bosslady, holding his knife to her throat. John urges Pesco to let her go. Pesco points out that then John will kill him, and he urges John to outsmart him. John lowers his gun and tosses it aside. Pesco notices Frank approaching the room on his monitors. Pesco says it's not a multiplayer game. Frank bursts in. Lt. Bosslady orders Frank to take the shot. John tells Frank they can take Pesco alive. The two of them exchange a barely perceptible nod, which is clearly the signal to go to Plan B. Frank insists they have to end it here. Pesco talks about how he's going to San Francisco next. Lt. Bosslady elbows Pesco, and Frank takes the shot just as John dives in front of the bullet and falls to the ground. Pesco is stunned, screaming, "Nooooooo!" Frank and Lt. Bosslady are freaked out. Frank runs to John's side as Pesco totally gets away. John is out. Wow, I bet he's dead. Maybe they'll have to change the name of the show.