That's the premise of Lifetime's new original movie Best Friend's Betrayal, which tells the story of Katie and Jess, whose once ideal friendship soon turns into a full-blown toxic nightmare.

Best friends Katie and Jess are inseparable and have always had each other's backs. When Jess begins a new serious relationship, Katie is unsure of the new perfect man and famous crime writer, Nick.

In LMN’s new thriller, a mother and daughter who are at odds uncover a shocking betrayal in the family. Watch “My Professor’s Deadly Secret” on Thursday, Oct. 17, at 8 p.m. ET on LMN.