Team Tennyson enjoy the biggest convention in town, but when a gawky costume store employee finds a familiar-looking helmet in the back of the store and tries it on, Ben is faced with the return of an old foe in a new form: Forever Knight!
The episode opens up with Steve and Bill announcing the cos con competition. Judges judge different costumes of the contestants. One of those contestants being Ben. However Ben didn't win. He exits the stage complaining. He questions why he gets booted off, while people wearing Forever Knight helmets get to stay. Gwen replies saying that every since Kevin's video went viral, Forever Knight caught a lot of attention. Max tries to reason with Ben, but Ben takes his words in the wrong. Ben transforms into Humungousaur and runs off. Max states that Ben doesn't need him to learn this lesson. He then walks off.
Max talks to a lady at a stand filled with mask. He questions the names of different masks. The lady then reaches to show him a "special mask", however it's missing. Max walks off, but then a kid wearing a Forever Knight helmet bumps into him, dropping his badge. Max catches up to the kid, but the kid dashes through, pushing Max out of the way. Max figures that the kid isn't the type of guy to knock a grandpa over.
Max walks into an exit, where the security guards followed the child. He then finds knocked out guards on the floor, one of them being controlled by Forever Knight's helmet. Max recognizes the Forever Knight. The Knight questions how Max found him, and Max admits that he just bumped into to him. Forever Knight recommends that he just walks away. Max allows him to pass by, Forever Knight walks by, but is tackled by Max. Gwen walks into the room looking for Max, only to find him wrestling a buff security guard. Gwen questions what's going on. A kid walks up, and Forever Knight suggest that speed would be more useful. He then takes over the kid. Max alerts Gwen that the helmet is Forever Knight, and he's looking for a new host for his consciousness. Max demands Gwen to find Ben while he keeps tracking Forever Knight. Max runs off and finds the kid, however Forever Knight's helmet is gone. The helmet then crawls by.
Back at the contest, the judges speculate Ben's new costume as Four Arms. They aren't impressed. Gwen alerts Ben that they have a problem. Gwen tells Max that she found Ben. Max tells him that he lost sight of Forever Knight. Ben questions who, and Max tells him that it's Forever Knight, and his helmet takes control over whoever is wearing it. Ben doesn't believe it. The helmet looks over to the Bill and Steve. Ben decides to go win the costume contest, instead of helping with the Forever Knight situation. Ben transforms into Omni-Kix Cannonbolt. Steve is then taken over by the helmet. He clears out the building, using the microphone. Cannonbolt complains, and then notices that it really was Forever Knight. As Forever Knight walks out, he runs into Cannonbolt. He attempts to escape, but Cannonbolt chases him down. They eventually make it to the top of the roof. Forever Knight is tired because of his new body. Cannonbolt Eventually, Max arrives, and Forever Knight jumps behind him, taking over his body. Forever Knight attempts to make an offer. He offers to let Max go, unharmed, in exchange for a clean exit. After almost throwing Max off of a cliff, Cannonbolt accepts. Before Forever Knight begins to leave, Gwen jumps on top of Max's head, taking the helmet off. Max then catches it inside of a bowl that was apart of Ben's costume. Max then calls Phil to see if he knows what to do. Luckily, Phil was there already. Phil states that he should interview everyone that the helmet latched on to, starting with the announcer, Steve. Steve sees the helmet and awards Phil a best-in-show ribbon for his costume. Ben then gets mad.
It is revealed that the Forever Knight is a technology construct with a consciousness that lives inside the helmet.
Phil takes Forever Knight to study him.
Max and Gwen are now taking the threat posed by Forever Knight seriously.
Max: Forever Knight is looing for a new host for his consciousness. You get Ben. I'll try to keep tracking him. Gwen: Right!
Max: Let me go! Forever Knight: You started this, now you're going to end it. Omni-Kix Cannonbolt: No! Forever Knight as Max: Maybe this will help you understand throwing someone's body into a time void has consequences. Steve: Hey. Wha-- What just happened? Forever Knight: Don't worry about it. Steve: Okay, nighty-night. Ugh. Omni-Kix Cannonbolt: What are you doing with my grandpa?! Forever Knight: I have a proposition for you, Tennyson. Obviously, I don't want your geriatric grandfather to be my host anymore than you do, but you have to understand, you've left me in a very difficult position. Grant me the dignity of a clean exit, and I'll return you're grandfather safe and sound. Omni-Kix Cannonbolt: What if I don't feel like making deals with robo-creeps? Forever Knight: I'm a very resilient construct. Unfortunately, I can't exactly say the same for my human hosts. Omni-Kix Cannonbolt: You're buffing! Forever Knight: If you're going to be like that, there's really no point in having this conversation. Goodbye. Max: Ben! W-What's going on? I-- Omni-Kix Cannonbolt: You did it! You win. Forever Knight: Excellent choice. I would like to say it's been pleasure doing business, but you're a horrible little monster, and I loathe you. Omni-Kix Cannonbolt: Ah, quit gloating! The sooner you get lost, the sooner I get my grandpa back! Forever Knight: Absolutely. Oh, and, uh, Tennyson...this should go without sayin-- Gwen: Someone forgot to count their Tennysons!
There is a background character who bears an appearance similar to Rook Blonko with a helmet.
The scene where Forever Knight takes control over Max was heavily cut down due to it being hard to animate, and too scary for kids.[KT 1]
It was stressful for Forever Knight to try to jump around between the congoers and make them perfomr the physical feats he was used to in the previous season. This is probably because he has a strict vetting process for bodies and only wants those in peak physical condition.[KT 2]