Dark Designs is the thirteenth episode of the Beast Wars TV series.
In some usual rocky terrain, the Maximals are disappointed to learn that their day's expedition has been a waste of time, as the energon they were searching for is inaccessible. Rattrap whines, saying the situation couldn't get worse, prompting an attack from the Predacons. The Maximals are at a clear disadvantage, but Rhinox triggers a rockslide that crushes all the Predacons.
Optimus Primal commends Rhinox's intelligent tactics, and the Maximals begin their return to base. Megatron also determines that Rhinox is a major threat to his operation and orders Tarantulas to capture the large Maximal. When Rhinox is a distance behind the other Maximals on the road home, the spider captures Rhinox and knocks the rhino out with some cyber venom.
A while later, the Maximals noticed their large comrade has disappeared. Rattrap activates his communicator, and are able to listen through Rhinox's communicator, overhearing the events in the Predacon base where Megatron uses "the Transmuter" to turn Rhinox into an evil Predacon. While the Maximals are concerned, Optimus Primal plans to wait a while before the Maximals make an effort to rescue their friend, yessssssss...
In the Predacon base, Megatron, and his new underling, Evil Rhinox, get down to plotting on how they can use Rhinox's knowledge to destroy the Maximals—but some technical problems with Megatron's computer halt the planning session. Rhinox is sent to check up on Scorponok's repair of the system (which was secretly vandalised by Rhinox). With no witnesses, Rhinox drops several tons of hardware onto Scorponok. When Scorponok's flattened body is found later by Megatron and Waspinator, they have no clue who committed the crime.
Waspinator deposits Scorponok into a CR chamber for repair, but flying away, Waspinator is hit with a heavy piece of weight pushed by Rhinox. The impact drives Waspinator into a state of dementia. This time, Rhinox's attempt at homicide is witnessed by Terrorsaur, who meets with Rhinox in private. There, Rhinox declines Terrorsaur's offer of partnership and insists that Terrorsaur stay silent. Later, Megatron discovers that Tarantulas and Blackarachnia have been poisoned. Still oblivious, a furious Megatron shouts out his confusion.
Outside of the Predacon base, Cheetor figures out Optimus Primal's plan: leave Rhinox as he is, so he'll run roughshod over the Predacons. But knowing that Megatron will eventually wise up, the Maximals get ready to mount a rescue. At the same time, Scorponok has been repaired, and he tells Megatron what happened to him. Megatron concludes that his little experiment has gone wrong, and decides to end it—and Rhinox as well.
Megatron confronts Rhinox, and assigns Scorponok and Terrorsaur to disarm the new recruit. By mentioning Terrorsaur's plotting, Rhinox is able to get the two Predacon goons to fight each other instead of himself, leaving them as easy pickings. With those two taken care of, he opens fire on Megatron, causing the Predacon to fall off his hover platform.
Rhinox taunts Megatron with a speech about who's the boss now, but Rhinox has stepped into the range of the Transmuter. Megatron reactivates the machine, converting Rhinox back to his regular good self. The Maximals blast their way into the base. Optimus Primal battles with Megatron, slicing off one of the Predacon leader's arms. A stray shot from the still demented Waspinator hits the Transmuter, and the Maximals grab Rhinox and evacuate while the Predacons take cover to avoid being harmed by the exploding machine.
Afterward, the Maximals relax. Rhinox admits that the Predacons have some serious personality problems, and the Maximals have a big laugh. Except for Dinobot.