Identity Crisis

TNG Season 4 Episode 18
Air Date: March 25th, 1991

The away team from a mission that Lt. Cmdr. La Forge went on when he served on the USS Victory start disappearing, La Forge and the only other remaining team member Lt. Cmdr. Susanna Leijten start investigating what happened that could have led to the disappearances. Originally they were investigating the disappearance of colonist of Tarchannen III.

It turns out that they are infected with a parasite that changes the DNA of the host to convert them into a primitive and translucent species that is driven to return to Tarchannen III. Doctor Crusher is able to figure out how to remove the parasite and saves Lt. Cmdr. Leijten and Lt. Cmdr. La Forge.

Quotes

"You know I'm not a threat. The others, Mendez, Brevelle, they don't exist as Humans anymore. But a part of you still does. You're not one of them yet, Geordi. I can help you if you'll just trust me. I know what's going on inside of you, the war you're fighting with yourself. Your Humanity slipping away. The instinct to run. It's overpowering. But they know how to beat it now, Geordi. Look at me! I've come back, Geordi. Let me take you back, too." - Lt. Cmdr. Leijten