Numbuhs 1 and 2 burst into Numbuh 5's house looking for her. They ask her father, Mr. Lincoln, what he did with her. He says she's just sick and she's up in her room sleeping. He has a batch a cookies for her when she gets up. They go up and check on her, and she is indeed sick. Numbuh 1 is really worried that an enemy might suck information out of her brain while she's in such a state. Numbuhs 1 and 2 decide to try to guard her. Numbuh 1 says they can't leave her side for a minute... and only a few seconds later they get hungry and so go to get some of the cookies from Mr. Lincoln.
The two boys start eating the cookies heartily, and Cree (Numbuh 5's older sister) comes in to get something from the refrigerator. Numbuh 2 seems to have a crush on her or something. Numbuh 1 scolds Numbuh 2 because Cree is a teenager and teenagers are the KND's worst enemies. Mr. Lincoln says that it seems they grow up so fast and it seems like just yesterday she was only a little girl...and then mentions something about her and her "brand-new training bra". Naturally, Cree is very agitated about this and starts beating up her dad.
Numbuhs 1 and 2 have no idea what a bra is, and Numbuh 1 also wonders what she's "training" for. They search the KND database for "bra" in their L.U.N.C.H.B.O.C.K.S. (Largely Undercover Nuclear Computer Handles Bologna Or Complicated Komputer Stuff), only to find nothing. Numbuh 1 then thinks that "bra" stands for something, so they try the "supercool name-inator program". It says that "BRA" stands for "Battle Ready Armor". Numbuh 1 becomes convinced that the adults have made some kind of new armor and that they're now training teenagers to use it. Numbuhs 1 and 2 vow to acquire a bra to analyze it for weaknesses. Numbuh 2 says it's a shame that Numbuh 5 has no idea that her sister is "wearing a bra right under her nose". Suddenly, they remember that had abandoned Numbuh 5, so they hurry back up.
The boys find Mr. Lincoln leaving Numbuh 5's room and questions him if he was trying to suck her brain for information. He says that he was just bringing her her medicine and that she's still asleep. Numbuh 1 looks inside and notices that Numbuh 5 is asleep. Numbuh 1 tells Mr. Lincoln that his story seems to check out, and that he can leave. Mr. Lincoln goes downstairs, talking about how kids say the darnedest things. Numbuhs 1 and 2 stand outside Numbuh 5's room. Numbuh 1 says they have to keep constant vigilance and they soon fall asleep. They awaken when Cree walks by, and, apparently "playing along" with Numbuhs 1 and 2 by asking how the "guarding" is going. Numbuh 1 tells Cree that they know she's wearing a bra and they'll put a stop to it. She leaves, muttering about her dad's big mouth.
Numbuhs 1 and 2 sneak into Cree's room and proceed to rummage through it. At last, they open a drawer and find the bras. They pull one out and don't understand how it can prepare people for battle, since it barely covers anything. Numbuh 2 says maybe when you put it on, it produces a protective shield. The two try to use it, but have no idea how to put them on. Numbuh 1 manages to get it on right (for the record, he is wearing it outside his shirt), but Numbuh 2 has it on all wrong. Cree hears the commotion and races into the room. When she gets in there, she is very outraged. "Are you crazy!" she screams. Numbuh 1 asks her tauntingly if she is worried that they will put her bras to better use. Cree then orders them to take the bras off. Numbuh 1 tries to activate the "Battle Ready Armor", but of course, nothing happens. Cree meanwhile grabs him and throws him around the room, again demanding that he takes the bra off. In no time, the boys are battered and Cree's room is destroyed. Numbuh 5, having heard the commotion, comes in and asks Numbuhs 1 and 2 what they're doing with her sister's bras. Numbuh 1 tells her that it stands for Battle Ready Armor and is a weapon. Numbuh 5 starts to explain what a bra really is, but then stops. She tells them to just leave, and Numbuh 1 warns her that someone might suck information out of her brain. Numbuh 5 orders them to leave, so they drop the bras and leave. Mr. Lincoln then comes in and says that Cree is telling her sister about bras. Both of them get annoyed and start beating him up and force him out of the room.
That night, while Numbuh 5 is asleep, a mystery person places a tube in her ear and sucks something out of her (it turns out to be information she had). This person, wearing a ninja outfit, quickly races off to a car and gives the person inside the information they got from Numbuh 5. The person inside the car is none other than Father with the Delightful Children From Down The Lane. The ninja deactivates the armor and is revealed to be Cree! She says that soon they'll put an end to the KND forever and ever, and they all cackle wickedly. Meanwhile, back at Numbuh 5's bedroom, it turns out that Cree sucked information out of a dummy. Numbuh 5 calls Numbuh 1 on her PIPER and tells him that they went for the bait. She then heads back to KND Headquarters.
The teens Lydia, Maurice, and Sheldon drive a tapioca truck in an attempt to deliver tapioca to a factory. Numbuhs 1-5 intercept the truck. Numbuh 2 beats them up and then, uses the MERRYGOROCKET, spinning the truck, until it crashes into the treehouse. The team congratulates Numbuh 2.
Numbuh 2 tells the story to his grandma, Lydia about the tapioca. Lydia thinks that Numbuh 2 is lying, and calls him "Tommy", making Numbuh 2 get to correct his name. Lydia gets mad, and begins to whack Numbuh 2 with the cane. Numbuh 2 tells Lydia that he is going back to the treehouse. Lydia tells Numbuh 2 that she has plans. By the time Numbuh 2 gets back to the treehouse, the team are mad at him for messing up. Numbuh 1 reminds Numbuh 2 that he was told to stop the tapioca truck, not crash it into their treehouse.
At night, Numbuh 2 begins to make another flying machine. Suddenly, the teens attack Numbuh 2. Numbuh 2 sees the alarm, and attempts to activate it. Before the teens attack, they feel pain, and Numbuh 2 activates the alarm. When the team arrives, the teens escape, and Numbuh 2 decided to make a story that he beat the teens. Numbuh 1 tells him that he is supposed to build inventions not stories. In Numbuh 2's house, Lydia, Maurice, and Sheldon became old, and discovered that the Anti-Aging Creme only works for a few minutes. Then, the three take the creme, revealing that the three were the teens with whom the KND battled.
In the morning at the treehouse, Numbuh 2 keeps telling the team that he saw the teens, but the team wouldn't listen. Numbuh 4 tells Numbuh 2 that he should have proof. The teens arrive to get the tapioca back. Numbuhs 1-5 attack the teens. Lydia grabs Numbuh 2, and suddenly she, Maurice, and Sheldon went back to their normal states. Numbuh 2 questions his grandmother on why she attacked them. Lydia tells Numbuh 2 that she only wanted to get the tapioca back. Upon finding the truth, Numbuhs 1, 3, 4, and 5 deicded to attack the three. Numbuh 2 tells the team that the three were so old that they wanted to have the tapioca back. Upon hearing this, Numbuh 1 orders his teammates to cancel the attack. Lydia warns the team never to let their guard down on old people, and the Senior Citizen Squad turns into a robot, and begins to grab the team. Lydia begins to talk to the team about the robot, while Sheldon keeps saying "There's nothing you can do about it." Numbuh 1 gets mad, and tells the three get taking the tapioca and leave.
Numbuh 2 went back to the treehouse. The team congratulates him for defeating the Senior Citizen Squad. Numbuh 2's story ends with Numbuh 2 in the Senior building with the tapioca truck crashed. Lydia begins to call Numbuh 2 "Liar Pants Tommy", making Numbuh 2 correct her on his name.