Plot summary
The Clones of the 501st Legion refuse to execute Jesse and Fives, and Krell sends them to engage Umbarans, disguised as clone troopers, that are preparing for an attack. The 501st Legion soon realizes that they are not shooting at Umbarans, but at the 212th Battalion of Clones. A dying Waxer reveals that Krell gave them the same orders. Realizing they have been betrayed, the Clones set out to arrest Krell, and a chase ensues. Clone Trooper Tup eventually manages to stun the General, who reveals he planned to ensure the Umbarans won the battle so that Dooku would make him his apprentice. The Clones agree Krell is too dangerous to be kept alive and decide to execute him; when Rex hesitates to shoot Krell, he is suddenly killed by another Clone Trooper, Dogma.
Credits
Adapted from Wikipedia contributors, List of Star Wars: The Clone Wars episodes. HTML formatting and reference markers removed.