Andrus Hagan

Andrus Hagan was a Betazoid science adviser who worked for Starfleet in an apparent civilian capacity aboard the starship USS Brattain in 2367.

When the ship fell prey to a Tyken's Rift and caused her Human crew to go insane and kill each other, Hagan was the sole survivor. An away team from the USS Enterprise (NCC-1701-D) found Hagan, himself either insane or rendered mute. Deanna Troi feared the same fate would befall her if the phenomenon happened aboard the Enterprise-D.

Hagan was treated in sickbay although Doctor Crusher wasn't able to help him. Troi communicated with him telepathically but received only information she wasn't able to interpret. 

Andrus Hagan Andrus Hagan