Silent But Deadly, Part 2 is the 21 episode of Grossology.
Fartor and his new apprentice, Far-Ty join forces to drill into the planet core and turn the earth into one big gas planet. Will everyone on Earth be forced to breathe noxious gas and join Fartor’s army of the fart-breathers or will Abby with Labrat's help be able to save her Brother and the planet from a lifetime of stink!
After being captured by Fartor and put in a big Dutch oven and going to the fart side Ty now as Far-Ty battles his sister winning with an ambush. The duo goes to a hydrogen sulfide filled lake to get out of their hover breathing suits and to discuss the plan. The plan for world domination. Meanwhile, Abby asks lab rat if he has a lead to where Ty might be when he sneaks up on lab rat and loses signal.
Far-Ty saying lab rats hiding and can't hide from a fart, lab rat comes out looking like a video game character. Far-Ty says video games don't count. Lab rat fires snot at the villain but miss and are soon caught in a fart cloud-filled room. Abby rushing in lets Labrat-free. Abby asks what was Ty's purpose for being there, Lab Rat replies that Ty wanted something with the lab's computer.
The scene switches to deep underground. Fartor saying the disaster of a result if the plan works. Lab Rat tells Abby what would happen if the greenhouse gasses which were mostly CH4 (methane) were released into the atmosphere.
Then Abby gets an idea and tells Labrat she will need some heavy duty modifications to the GRS-1 Lab Rat gets to it. Underwater they get another sneak attack from Far-Ty. As their sister-brother bond breaks apart, she tries to fix it to turn Far-Ty into Ty again by saying that they were a team and always were a team.
Then she gets a good idea to stop Far-Ty and says it's time to cook up some seafood. They later successfully defeat the giant robot. Far-Ty getting mad says to never trust anything that doesn't fart.
Meanwhile, at the gag lab rat finds hope in stopping the gas release and curing Ty. Then the fart breathers start drilling and a 10-minute countdown is then activated to signal the release of the gasses and with limited time to save Ty as he is still immune to being a villain.
As moments pass they do a video explaining their plan, but Abby won't go down without a fight and heads underground to confront her villainous brother Far-Ty. She tells him that he has to fight the fight the Fart side, though Ty response to her that he likes being Far-ty.
Abby then jumps on Far-Ty and takes out his suit's methane tank and replaces it with a fresh air tank, possibly oxygen. Ty goes unconscious for a few seconds but then regains consciousness and states his name is Far-Ty.
Then the timer says one minute and greets Far-Ty and Abby. Abby asks why didn't the fresh air cure work wondering just how he is so immune, unlike Fartor.
Far-Ty gives Fartor the bacteria device that would've spoiled their plans. Then Fartor orders Far-Ty to take to the gas pump.
Abby wants Ty to think about what he is doing, letting him think of the aftermath, then in a minute Ty finally realizes where he belongs and tells Fartor they are family together as brother and sister they defeat Fartor and save the city from a silent but deadly stink.
Ty is then taken back to the gag lab for full analysis to check for any signs of Far-Ty, the results are negative and he is given the all clear. Their adventure ends there, until Insectiva arrives and Ty a headstart on Abby.
The main gas that is used in this episode is CH4, this is Methane gas.
The countdown timer for the end of the city and possibly the world is 10 minutes, beacuase of suspense.