Still upset over Matt and Mariana, Nick sits in the parking lot and musters up the courage to go into school with a gun he keeps in the glove compartment.

Callie tells Lena and Stef the truth about sleeping with Brandon. Including the fact that Rita already knows about it and that the rest of the world might too.

Matt notices that Nick has been behaving strangely and questions Marianna about it. She receives a text message from Nick, where he tells her that he saw her kissing Matt. 

Jesus and Emma flirt even though both were previously involved with other people

Stef and Lena wonder why Callie didn't tell them about Brandon before, but they can't have a discussion because Mike interrupts them to inform them that there was a fire at Nick's father's warehouse.

Nick meets Marianna on the school's rooftop, and she tells him that the kiss between her and Matt didn't mean anything. Nick seems reluctant to believe her. He's about to pull out a gun when, a janitor interrupts them and tells them to get back to class.

Mike and Stef suspect that Nick may have been responsible for the Arson, and are at the school hoping to locate him and ask him questions. NIck's father arrives at the school, and reveals that not only did he not give the school permission to use his warehouse for the school play that Brandon threw last season, but that the school is liable. 

Mike confirmed that no one has seen him on campus and they go to see if his car is there. No one is able to locate Nick on the school campus. Everyone runs to the parking lot to see if Nick's car is still where it was parked, but it isn't. Stef and Mike ask Nick's father if Nick  has access to a gun. His father says  that he has a weapon, but it's locked up and kept  in the trunk of his car. Everyone checks the car and sees that the gun isn't there anymore. 

Callie confesses to Brandon that she told their mothers about their sexual intercourse. Alarms sound off and the school goes into a Code Blue alerting them that someone has a gun on campus. Brandon takes the lead in the classroom enacting all of the protocols.

Marianna is still in a bathroom when the alarm goes off and drops her cell phone into the toilet. She tries to get into any of the classrooms but instead has to go back and hide in the bathroom.

Stef orders for a Swat team. 

Lena is in the office and says that she hasn't heard anything from Callie and Brandon. Nick tells Emma that Nick seemed upset and thanked him for being a good friend earlier and that it seemed final. Mr. Stratos tries to call his son and leaves a message for him begging him not to do anything stupid.

Jude sends a text message to Connor. One of his classmates scolds him.

Lena tries to go looking for her, but Mike hold her back and tells her that she can't. It's too risky. They're afraid that she may be with Nick.

Brandon and  Callie have a quiet moment. Callie apologizes to Brandon for telling their mothers, and Brandon tells her that she doesn't have to apologize.

Stef and Lena and Jesus reunite when the Swat team escorts Jesus and Stef outside. Stef hugs them both and sends them to safety. Both are still concerned that they haven't heard anything else about Marianna.

Marianna is in a bathroom stall, standing on a toilet seat alone and afraid. She hears noises that sound like someone is coming closer to her from down the hall. She suddenly hears a gunshot.

At the sound of a gunshot Stef breaks protocol and runs towards the building. 

The swat team bursts into Brandon and Callie's classroom and the substitute teacher aims a gun at them. The substitute apparently brought a gun to school. They remove the gun and direct the kids outside.

Swat tells Stef to come with them. Stef comes out of the school guiding a shaken Mariana to the rest of her family, and the Foster family hugs.

Swat searches the entire school but hasn't found Nick there. They tell everyone that they should go home.

Back at the Foster house Nick is going through Marian's stuff in her and Callie's room before lying on Mariana's bed. The Fosters arrive home, but Stef tells them to hold off on going inside until she does a quick sweep of the area just to be safe. Nick is nowhere to be found.