Crossing the Rubicon is the forty-eighth episode of the Beast Wars TV series.
Some distance from Mount St. Hilary, Blackarachnia is setting up some equipment that will convert her into a Transmetal 2. However, Silverbolt detects Blackarachnia's energy signature, and, not understanding, pulls her from the machine. As Blackarachnia berates Silverbolt, she short circuits. Heading to the Maximal base, Rhinox concludes that the shell program is starting to degrade, and will erase her core consciousness if not treated soon. He can remove the shell, but it's never been done before.
Wandering off to think, Blackarachnia is followed by Silverbolt. She maintains that she's still a Predacon, and that becoming a Maximal scares her. Silverbolt points out that she's only a Predacon due to Tarantulas, and deep down, she is one of the good guys. The touching moment is ruined when Blackarachnia short circuits again.
In the lab, Blackarachnia has decided to go through with the procedure. Before she does, there is one last thing to do: transfer the access codes to the Ark to Optimus Primal, thinking that he'd have the best chance to keep them from Megatron. They begin the shell removal, but it has safe guards that will destroy Blackarachnia's core consciousness. Rhinox is able to destroy the first one. At his lair, Tarantulas discovers the removal process. He contacts Megatron, informing him of the situation. Megatron notes that such an act risks destroying Teletron 1's access codes, and conclude that she gave them to Primal. Tarantulas informs Megatron of his safeguards, but the Predacon leader decides to cause a little more trouble.
Inferno, Rampage, and Quickstrike are sent under Tarantulas to attack the Maximals. Optimus leads Cheetor and Rattrap in the defense of the base. Rhinox is almost finished, but two more power surges head for her core consciousness. Rhinox blasts one, but Tarantulas fires a rocket which causes Rhinox to miss the other surge, which hits Blackarachnia's core consciousness and extinguishes her spark. Rhinox leaves to inform Optimus and allow Silverbolt to be alone. Upon leaving, Silverbolt snarls out "Tarantulas…".
Detecting that his creation is dead, Tarantulas orders the Predacons to break off, as Rhinox tells the others. Gathering around Blackarachnia, they express their regrets over not giving her their full trust, if only for Silverbolt's sake. As Rattrap notices that the Fuzor is absent, Primal realizes what he's planning to do, and the Maximals head to stop him. Unseen, the Transmetal Driver begins to glow. Tracking down Tarantulas, Silverbolt easily defeats him and, with the villain unconscious, prepares to execute him. However, Rampage has been watching this and defeats Silverbolt. Preparing to strike the killing blow, Rampage is stopped—by Blackarachnia, now a Transmetal 2. Blackarachnia quickly defeats Rampage, and takes Silverbolt back to base.
In the control room, Blackarachnia explains to the Maximals that she saw only darkness, then a light, and thought Silverbolt was in danger. Primal points out that her actions weren't very Maximal, but Silverbolt express their gratitude at her return. Blackarachnia warns Silverbolt to stop rushing after her, but to show no hard feelings, kisses him, sending a power surge through him and disorienting him.