20 Horror Films Where The Hero Teams Up With The Villain

In Texas Chainsaw 3D, Heather Miller heads to Texas after inheriting property from a distant relative. After studying her family history, Heather realises she's related to the murderous Sawyer clan and that the chainsaw-wielding cannibal, Leatherface, is her cousin.

Naturally, this revelation causes Heather to become hysterical, especially after the skin-wearing lunatic chases her. However, she feels empathy towards Leatherface when she finds out the Sawyers were executed by the townsfolk, meaning she's the only family he has left. 

When Officer Hartman discovers the pair's connection, he vows to kill them both and wipe out the Sawyer bloodline for good.

As Hartman confronts the remaining Sawyers, Heather no longer sees Leatherface as a psychopath but as her own flesh and blood. And while she has the chance to run, she can't stand by and watch Hartman finish Leatherface off.

Refusing to let the last of her kin die, Heather tosses him his chainsaw and utters the immortal line, "Do your thing, cuz." Armed with his signature weapon, Leatherface lops off Hartman's hands before tossing him into a meat grinder. 

By the end, Heather agrees to care for her cousin to his dying day, fully embracing her disturbing lineage.