He introduces himself as Garrett, who was originally from Arus but escaped when Zarkon first attacked. Then, the mechanical malfunction on the blue Lion manifests into an explosion, to which Garrett was standing near. He does an incredibly acrobatic leap to escape the fire and sparks and shrugs it off as lucky. The others think it's more than luck. Coran invites him back to the Castle.
Over dinner, Coran grills Garrett on his parents and the nature of his escape. He begins to wonder if this young man isn't his own son. Coran thinks back to sending his wife and infant son away from the Castle, and remembers he gave the boy a necklace that was a family heirloom to remember him by. After dinner, Coran can't stop obsessing about his lost wife and son, and wondering if the man is his long lost son.
Later, he notices a scar on Garrett's arm, and remembers his son had one in the same spot. Still, Coran can't stop thinking it's only an amazing coincidence - just too good to be true. And for whatever reason, they've taken in this man and are training him to pilot Blue Lion...??? I guess they must really like him, eh? Donning Sven's old uniform, the newbie does surprisingly well in the Lion and looks to be Allura's replacement.
Exiting the Lion after his practice run, Garrett casually loosens his uniform collar and out spills the necklace with the telltale pendant. Coran can contain himself no longer and reveals he is Garrett's father. Much tears and a happy reunion follow. But nobody thinks to question how a kid raised on a moon knows how to shoot and pilot like he's been doing it all his life. Damn Gary Stu all to hell! Sorry, but if someone wrote this stuff as fan fic, we'd all be barfing right now lol
But a quick look at what's going on in Castle Doom reveals the awful truth. Garrett is an imposter designed by Haggar after she learned about Coran's real son and his indentifying marks. They even gave Garrett a magic ring that will be used against Coran and incapacitate him. With Coran out cold and an emergency brewing, the team is stuck for someone to man Castle control and guide them. Despite Lance's worries, Keith elects Garrett to be the one to stay behind.
He does lead them to a few of the incoming ships, but craftily keeps them from the main fleet. Lance still smells a rat, and when Keith questions Garrett as to why they haven't found the fleet yet, he tells them they're too slow. With the team distracted, Garrett calls Planet Borra - which happens to be where the alliance is keeping the powerful Pulsar Cannon - and requests permission for Voltron to land. However, it's actually Lotor and his fleet that land. Not good.
Lotor, after stealing the canon, wants to plant it on Arus and sends out a Robeast to take care of Voltron in the meantime. Voltron takes a hideous beating from the robeast, falling back down to Arus in what might be defeat. Meanwhile, Lotor is getting the canon in place on an Arusian mountain top. Garrett has taken over the Castle.