Don’t say I didn’t warn you, this has spoilers!

As usual scifi.com uploaded the epsiode synopsis before the show airs. http://www.scifi.com/lexx/episodes/season4/xx.html

where xx represents the number of the epsiode.

4.13 “769”
790 makes a deal with Prince to help him get the key to the Lexx in exchange for having Xev and Stan killed. Part of the plan includes 790 being attached to the modified body of a mothbreeder which just happens to also have the key to the Lexx. 790 proclaims he is now to be called 769. (On the Cluster, a 790 robot attached to a body that kept its original head was called a 769).

On the Lexx, Bunny pulls a gun on Xev and Stan shortly after Kai is put into his cryotube to preserve his protoblood. Stan and Xev convince her not to kill them. 769 returns to the Lexx hoping to have sex with Kai. When Kai awakes, 769 gets so excited that the key leaves his hand and disappears into Bunny’s raised palm. Bunny then kicks 769’s robot head off the mothbreeder’s shoulder returning 790 to his original bodyless state.

Kai takes off in a moth for Earth to kill Prince once and for all, but Prince and Priest are already on board the Lexx and quickly overtake Xev and Stan. Happy to see each other again, Priest and Bunny share an intimate moment. Bunny unknowingly loses the key to the Lexx again. Before Prince can harm Xev or Stan, Kai returns and kills him. Priest and Bunny escape in Moth to Earth.

4.14 “Prime Ridge”
With no way out of the solar system, Xev, Kai and Stan buy a home and settle down in Prime Ridge, Ohio.

4.15 “Mort”
On the run from the law, the Lexx crew hide out in a funeral parlor run by a Dr. Frankenstein-like mortician.

4.16 “Moss”
Xev, Stan and Kai are captured by a renegade FBI agent.

4.17 “Dutch Treat”
The crew must find food for the Lexx before it starves to death.

4.18 “The Game”
Kai plays a game of chess against Prince. The outcome will determine whether Xev and Stan live or die.

4.19 “Haley’s Comet”
A radical group of kids board the Lexx with a hidden agenda.

4.20 “Apocalexx Now”
Kai and Xev journey upriver in Vietnam to rescue Stan.

4.21 “Viva Lexx Vegas”
On the way back to the Lexx, the crew stops in Las Vegas where a killer Mummy is on the loose.

4.22 “Trip”
The crew is deceived by a gift that causes bizarre hallucinations

4.23
The alien threat makes Japan its first target in a plot to destroy the Little Blue Planet.

4.24 “Yo Way Yo”
Kai, Xev and Stan race against time to defeat the aliens and save the planet.