Changing of the Guard is the forty-second episode of the Beast Wars TV series.
Rhinox is in the process of engineering a way to use Teletraan I's forcefield to protect the base. But mixing Autobot and Maximal tech is difficult, and the machinery fails. With that trick failed, Optimus Primal puts together a plan to salvage the Maximals' old force field module, Sentinel, from the wreckage of the Axalon. Depth Charge refuses to respond to any contacts. So instead the Maximals will use a subaquatic stealth vessel—a single-occupant submarine developed by Blackarachnia. Rattrap is assigned to pilot the submersible, over his usual handful of whines and complaints.
Silverbolt delivers the submarine to the Axalon's resting site. Under the lake, Rattrap is surprised to find himself having a good time exploring the water and passing by schools of fish to the sound of a jolly tune. The tune changes as Rattrap finds the fallen corpse of what used to be the Maximals' home. He slowly enters, looking through the darkened hallways. He finds Sentinel, and carefully begins to extract it—and is suddenly frightened by an eel who was hiding in the machinery. As he calms down, his radar detects something else approaching, and he realizes it's time to panic for real. Rattrap frantically tries to escape the Axalon, but a massive claw emerges from the darkness and seizes the submarine—Rampage has found him.
Rampage squeezes the entire ship, threatening to crush it completely. Luckily, Depth Charge, still hunting Protoform X, shows up and blasts him away, freeing Rattrap. Depth Charge agrees to keep Rampage busy while Rattrap continues his mission. He escapes the Axalon just as shockwaves from the battle cause the ship to fall over a ledge and plunge deeper into the lake. Rattrap surfaces and finds a worried Silverbolt, who starts to carry the submarine home. But Waspinator arrives, causing Doggybot to drop his passenger and cargo.
While Rampage and Depth Charge continue their match underwater, on the beach, Quickstrike sends Waspinator to take Sentinel back to the Predacon base while the Fuzor takes care of the two Maximals. But Quickstrike ends up crushed by Rampage, tossed out of the water by Depth Charge. Silverbolt tries to convince Depth Charge to help recover Sentinel, but as usual, Depth Charge has no interest, wanting only to execute Protoform X, who has snuck away during the few seconds of conversation.
Together, using some incredible aerial acrobatics, Rattrap and Silverbolt steal back Sentinel from Waspinator... just when things were looking up for the poor Predacon. But Inferno pushes a tree into Silverbolt's path. Silverbolt passes Sentinel to Rattrap, who races away with it. Depth Charge hears explosions in the distance and decides to go help.
Unrelenting, Inferno blows up a bridge in Rattrap's path, causing the rat to plunge—back into Silverbolt's arms. But the two Maximals crash into the incoming Depth Charge, and drop Sentinel into Inferno's hands. Thanks to Depth Charge's ill-timed arrival, the Maximals have lost.
At the Maximal base, Rattrap and Optimus Primal chew out Depth Charge for getting in their way and handing another major strategic advantage to the Predacons—but he did save Rattrap's life (which Rattrap initially left out, and was very begrudging to admit). Primal offers Depth Charge a place with the Maximals so mistakes like this can be avoided in the future, and Depth Charge agrees to consider it.
Meanwhile, in the Predacon base, Megatron activates Sentinel, encasing his base in a protective force field.