(NBC) When U.S. Army Capt. James Van Thach returned home from Iraq in late 2008, he began to worry that the darkness might not ever lift.

The pain from his war injuries was constant, but his thoughts hurt him even more. He felt embarrassed about so many things: his marriage unraveling and ending; his inability to use his law degree after sustaining a traumatic brain injury; his need, at age 33, to move in with his parents so they could care for him and help him take 21 pills a day.

It wasn't until a calm, loyal friend named Liz entered his life in 2012 that Thach could step back into the light again. Liz is a highly trained service dog, and she only has eyes for Thach.

(READ the full story, with photos, from TODAY)