On The Orville Season 2 Episode 9, the crew must prevent the Kaylon fleet from arriving at Earth to begin their extermination of all biological life forms.
The crew is being held in the shuttle bay but kept alive. The Kaylon share their plan which is that the bridge crew will pretend that Kaylon has agreed to join the Planetary Union and get Union Central to lower the Earth's defenses. If Mercer and his team do not comply, the rest of the crew will be killed. When they encounter another Planetary Union ship, Mercer attempts to pass a coded message on but Kaylon Primary is aware and the other ship is quickly destroyed. An ensign is air-locked in front of Mercer as his punishment.
Isaac tries to intervene and the Primary questions his motivations.
Grayson decides to attempt to contact the Krill for aid. She and Malloy escape the ship in a shuttle, pursued by one Kaylon vessel. The Krill they find don't believe them until the Kaylon ship arrives and destroys two of the Krill ships.
Yaphit and Ty attempt to get a warning message to Union Central. Kaylon guards arrive and despite Yaphit's best efforts, Ty is taken. Isaac is brought to the Primary and ordered to kill Ty. Instead, Isaac turns against the Primary and the other Kaylons and enacts a plan to deactivate all the Kaylons aboard the Orville, including himself.
The Orville and the Kaylon fleet arrive at Earth where the Planetary Union fleet awaits them. The battle begins, with the P.U. ships sustaining a lot of damage. The Krill fleet arrives and saves the day, sending the Kaylons into retreat.
The Krill leave after the battle, leaving the door to peace talks open. Isaac is reactivated by the Orville crew and Mercer petitions to let him stay with the Orville as a crew member with no restrictions as he has no home anymore.
On The Orville Season 2 Episode 9, Ed and the crew of the Orville seek to derail the Kaylon attack on Earth and the Planetary Union.