Deep Metal is the forty-first of the Beast Wars TV series.
On Earth, in their new base in the newly fortified Mount St. Hilary, Rhinox has trouble working with the hardware salvaged from the Axalon. Optimus Primal considers this as another reason they need help from the Maximal Elders to arrive soon as possible, but Rhinox doubts the help is coming. Yet as they speak, help from Cybertron is indeed coming—just not exactly the kind they were hoping for. In a sector declared off limits by the High Council, a mysterious Cybertronian hunts for Protoform X. However, his ship is soon pulled into a transwarp portal that suddenly appears.
Outside the mountain, Inferno leads Rampage in a planned invasion of the Maximals' current base. But the stranger entering Earth's atmosphere distracts Rampage away from the exercise, leaving Inferno to attack the Maximals on his own. The fire ant is easily defeated by a rock. It was a pretty big rock.
Cheetor also notices the spacecraft descending into Grid Alpha Seven and flies to check it out. Receiving a radio contact from Cheetor, Primal heads out to join him. Cheetor watches the spacecraft landing in a body of water, but in the middle of a radio update to Optimus, Rampage fires a rocket to blast the Maximal out of the air, saying this is between him and the visitor. Underwater, the newly arrived Maximal, Depth Charge, scans a manta for his beast mode and leaves his transport, eager to hunt Protoform X. Surveying the area, Depth Charge finds Cheetor sinking to the bottom of the water. Depth Charge rescues his fellow Maximal, but only gives his name and not much of anything else when he strands the cat-bot on an island.
Underwater again, Depth Charge homes in on his quarry's signal. However, what he finds are nothing but rocks. Rampage then jumps from the ground and latches onto Depth Charge, greeting the Maximal as his "old playmate". The two battle, and Depth Charge lifts their combat into the air. Rampage blasts the manta and forces the fight onto the beach, but finds himself impaled on a stalagmite. While the two giant Transmetals are disabled, Primal arrives and meets with Cheetor, who fills in the Maximal commander on what's happened and tells him of Depth Charge...a name that Primal recognizes.
Rampage heals and approaches Depth Charge, but Depth Charge awakens and fights back. The two show off their abilities, but Depth Charge wins the fight by throwing his tail-spike into Rampage's weaponry, causing explosive feedback. Quickstrike shows up and fires at Depth Charge with a disabling poison blast, but Primal easily takes out Quickstrike. But thanks to Quickstrike's interruption, Rampage has had the time to sneak away. Primal and Cheetor bring Depth Charge back to their base.
As Depth Charge heals, Primal and Rhinox explain that Depth Charge was in charge of security for Colony Omicron before Protoform X devoured all the other inhabitants of it. Seeking vengeance, Depth Charge spent four stellar cycles hunting X before he captured the maniac and petitioned the High Council to find some way of executing him. Instead, Protoform X was placed on the Axalon to be dumped. Depth Charge thus followed the Axalon through transwarp by tracking X's energy signature, intending to finish the job he started.
Depth Charge awakens repaired and exits the CR Chamber. He blows off the Maximals, showing obvious contempt for Optimus Primal. He makes it out of the room before stopping short at the Ark and the Maximals explain the gravity of the situation. He leaves to go hunt Protoform X, with no interest in the rest of the Beast Wars and saving history. Cheetor wonders if he'll be back, and Optimus says that before Rampage, he would never have left.
Meanwhile, Rampage destroys the vehicle Depth Charge used to come to the planet.