Unlike most episodes of 'Glee,' this one opens with a grim disclaimer that the episode will be depicting school related violence. And boy does it.

While Mr. Schuester (Matthew Morrison) is telling the club about their competition for Regionals, Brittany (Heather Morris) bursts in an announces that an asteroid is heading toward Lima, Ohio. An asteroid that she has dubbed Tubbington Bop after her cat. She says with the end imminent, she plans to spend her time with who she loves the most, the real Tubbington while Sam (Chord Overstreet) listens to her sadly.

Inside the choir room, Brittany's theory has given Will an idea for the club's weekly assignment: last chances. He urges them to finish their unfinished business and either sing for the last time or sing like it will be their last time.

As they leave, Ryder (Blake Jenner) tells Jake (Jacob Artist) all about his online girlfriend Katie and how he's in love with her. He also tells his friend that he saw her in the hallway while he was in class and that he desperately needs to meet her.

Sam watches sadly as Brittany gushes over Lord Tubbington, telling him she loves him. In response, he suggests she bring the cat to school and sing a song to him so everyone can see and feel her devotion.

Ryder approaches Katie in the hallway, who seems excited yet confused that he's talking to her. Without getting too much into their relationship, he invites her into the glee room with him and serenades her with 'Your Song' by Elton John. After the song, she praises his singing but wants to know why he chose her. Ryder starts to explain how he fell in love with her through instant messaging, but she reveals it was never her. When he shows Katie their messages she tells him those are pictures of her but someone was just pretending to be her.

Out in the hall, Ryder blames Jake and Marley (Melissa Benoist) for catfishing him. When they explain it wasn't them, a visibly distraught Ryder leaves in a huff saying it had to be someone close to him.

In the auditorium, Sam sings Extreme's 'More Than Words' to Brittany while she sings the same song to her cat.

At the end of the day, Will finds Coach Beiste (Dot Jones) in the locker room, having made them a 'Lady and the Tramp' inspired meal to enjoy before the end of the world. While drinking and thanking Will for making her feel like a lady that one time he kissed her, she says that she wants Will to be the last man she's ever with since they're both single. When he admits he and Emma (Jayma Mays) are back together, she tearfully leaves.

Ryder's phone goes off in class and it turns out to be whoever Katie is, admitting to lying to Ryder in an attempt to get close to him, but not admitting their real identity. When Ryder says he will stop talking to them if they don't reveal themselves, they agree to meet the next day in front of the choir room.

Brittany admits that the asteroid she spotted in her telescope was really just a dead bug and her telescope was a Pringles can. In response, she disbands the Astronomy Club. Becky (Lauren Potter) tells Brittany that she admires her and they should make a pact to never graduate because the world is a scary place. Brittany agrees that the world is frightening, but says that they both need to move on.

The kids are in the glee room when they hear two gunshots. Everyone hides and Will tells them to start texting and tweeting to explain to the outside world what is happening. As more gunshots go off and someone desperately tries to get in the choir room, Will tells them he loves them. Sam wants to find Brittany who is in the bathroom and Blaine (Darren Criss) is equally worried about Tina (Jenna Ushkowitz) who is also M.I.A.

While Brittany is hiding in a bathroom stall, Marley is trying to desperately contact her mother and Kitty (Becca Tobin) in the heat of the moment admits she was trying to make Marley think she was gaining weight during their production of 'Grease' but she was really just taking in all her clothing. Sam is being held back by Will and Coach Beiste, who tell him by trying to get to Brittany he is putting everyone in danger.

Outside, Tina is desperately trying to get Principal Figgins (Iqbal Theba) to let her inside to get to her friends in the choir room. Inside, Artie (Kevin McHale) is videotaping everyone to send out their last messages just in case, until Sam makes him shut it off.

Brittany is in the bathroom when she hears footsteps. After a few terrifying moments, the door opens and she rushes into Mr. S's arms.

An upset Ryder calls "Katie" but a phone inside the choir room goes off instead. Ryder is torn between wanting to find out who is catfishing him and wanting to save his friends, but after much urging he shuts his phone off.

Will and Brittany run into a SWAT team in the building who give the all clear, and the glee club fully reunited (minus Tina) share a group hug.

The next day the police are searching lockers and a metal detector have been set up. Will is concerned that the children have lost their innocence and says the student who shot the gun will most likely be suspended. It is at this point that Sue (Jane Lynch) tells the audience that there were no casualties but that it wasn't a student's gun at all.

Inside Figgin's office, Sue tells him she had a gun in the school for safety reasons and she was doing her daily safety check when it accidentally went off, going off another time after it hit the floor. A grim Figgins tells her he "has no choice" while Sue regrets that this is all she'll be remembered for.

Tina tells Blaine she's upset she couldn't be there in the choir room in case her friends needed help or a goodbye was required. She cries, they hug, admit they love each other and Blaine tells her despite what she thinks, she was there in spirit. They walk off holding hands.

Will shows Coach Beiste that he set her up an online dating profile and thanks her for being there for him during the accidental shooting. As they smile at each other, a match shows up: Ken Tanaka (Patrick Gallagher) the school's former gym teacher and Emma's first husband.

In light of recent events, Sam tells Brittany they should start a fake family and pulls a cat out of his backpack whom he has named Lady Tubbington.

Will confronts Sue, saying bringing a gun to school is out of character even for her. As he talks, we flashback to Becky in Sue's office saying she's scared about one day having to leave. In her lap is her dad's gun. When Sue tries to extricate it from her, Becky accidentally pulls the trigger and it goes off, which it does again when it hits the floor. As Becky cries, Sue promises she'll take care of everything.

In real time, Sue asks Will to watch after Becky.

Ryder stands outside the choir room waiting for "Katie," but when she never shows he runs to be with the New Directions who are singing John Mayer's 'Stay.'

The episode ends with clips from Artie's video of everyone saying their tearful goodbyes.