When Allura loses contact on Chemara's moon Cryo while racing back to the castle with the others, a young humble Arusian man named Garrett rescues her. Coran eventually recognizes him as his long-lost son by a pendant he wears, and the Voltron Force welcome him and are set to let him pilot the Blue Lion. But none of them are aware that he is a spy from Haggar, until he locks all who can help the five out of the control-room and works them into a trap where they will be attacked by the stolen Polsar Canon as well as a typical robot enemy.
