During a rousing good time at the Black Penny, Sam gets down on one knee to ask Oliver to be his best man. The answer is an enthusiastic yes. Unfortunately, Andy’s enthusiasm for the evening takes a nosedive when she realizes she can’t find her engagement ring. She doesn't want Sam to find out, and enlists Traci's help for the search.
Commissioner Santana is somewhat upset with Noelle for not informing him that she placed an Internal Affairs officer inside 15 Division. He wants all the information she's accumulated ASAP. That could be a problem. Noelle lets Sam know that, according to Juliet’s report, the only person who could have possibly planted a bomb in the evidence room is Oliver.
Sam, Andy and Dov work to clear Oliver's name so a possibly-corrupt Santana can't pin the bombing on him. The device came from an explosives dealer named Chris Klem. He and his daughter, Ava, have been missing for three months. Andy and Sam check out their abandoned house. A neighbor who has been caring for the family dog says Chris had a big shouting match with the police officer who brought his daughter home one day. And that police officer just happens to have been Detective Norman, the same officer leading the investigation into the family’s disappearance.
Sam realizes that his best friend now looks like the perfect scapegoat, because he got help from the commissioner back when Oliver’s daughter Izzy was caught with drugs. Dov is able to track Ava down online by challenging her to a World of Warcraft game. The race is on to find her before the game is over. On the way, Sam begins to ask questions about Andy's ring. As she tries to stall, Sam reveals he found Andy's ring. He bought her something to make sure she'll never lose it again... a quacking locator device!
Sam and Andy track down Ava at the university library. The girl is not going down without a fight. She makes a scene to ensure a crowd of witnesses protect her, because she believes Sam and Andy aren’t real cops. She runs, unintentionally leading them to her dad. Chris Klem is also extremely paranoid about them because they're cops. Sam explains that they need his help to save their friend, who is being set up by the same police officer who Klem is running from. Klem eventually believes they are there to help him. He gives up the name of the police officer he sold the explosive materials to before the evidence room bombing. He claims that police officer was Oliver Shaw.
The rest of 15 Division is on the case of Evan Malone, a young boy who has been missing for several hours. He was last seen talking to a neighbor, Reece Gray, who turns out to be a registered sex offender. But Gray claims he received the label unfairly, from an incident that happened 20 years ago. Gray grants the police permission to search his apartment, which turns up nothing. When Evan’s father arrives, he reveals that his son is on the autism spectrum. Evan's mother admits she hadn't mentioned it because she believed the police wouldn't put out an AMBER alert for her son.
There was a pile of old junk in front of one of the neighborhood homes. Oliver wants to find a van that was scheduled to pick up the stuff. He and Nick track down the driver at a junk yard. In the back of the truck, Oliver finds Evan's book, about a magical wardrobe, and makes the connection. One of the items picked up was an old wardrobe and Oliver realizes that Evan climbed inside it and got locked in. He finds the kid unresponsive but is quickly able to revive him. Oliver holds the frightened child close, and gently rocks him back and forth.
Oliver is scheduled to play drums with his daughter’s band at Joe’s Fish Tank that night. He's invited Dov and Chloe to attend up. He gets completely blindsided by Sam and Andy’s revelation that he’s been connected to the evidence room bombing. There’s a report being submitted implicating him right now. Oliver is stunned, and devastated. As the reality of the situation sinks in, Oliver begins lamenting the 20 years he's neglected Izzy to devote his life to the job, and saving the world. He slowly sets his badge on the desk, and tells Sam and Andy to give it to Jarvis for him. Then he heads off with his daughter to play in her band.
Meanwhile, Traci has been tasked with driving Chris and Ava Klem to a safe house. She listens to the story of why they went on the run. Fear was the ultimate motivator. Then Traci's phone rings, and Klem begins to panic. He's seen Steve's face pop up on the screen. That's "Oliver Shaw," the man he and Ava were running from, the man who bought the explosives that were used in the bomb! Traci begins to realize that she might not know her boyfriend as well as she thinks she does.