Libby Strauss was a resident from Tucson, Arizona.
In 2016, Libby came to Gunnison, Colorado with a friend to pay the town a visit, only to become the first out of six people to disappear in the area. Her friend Cori witnessed a mutant creature with green eyes carry her off, and when she tried to pursue them, she discovered that Libby had been turned into a green-eyed mutant.
Libby's mysterious disappearance drew in the attention of Sam and Dean Winchester, who disguised themselves as FBI agents and paid the local sheriff a visit. Sheriff Tyson did not find Libby's friend a reliable source because the girls had been high on cannabis.
Dean personally questioned the friend, Cori, who insisted that she had not been hallucinating. Cori began describing the creature as "naked and pale", and noted that it was "junkless". Cori had found Libby just standing still, shaking while making an unusual buzzing sound. A flashback showing Cori's encounter with Libby revealed that Libby displayed hostility towards her friend and did not respond to words.
When Dean decided to look for Libby in the woods, he found her, only to be ambushed by another creature and nearly get killed if not for the timely arrival of Jesse and Cesar Cuevas. The two men informed Dean and Sam that they were dealing with Bisaan.
While in the Bisaan lair, Dean found Libby's body shortly before being attacked by one of the male Bisaan. After killing the males, Cesar and Dean noticed that all of the women were already dead and were visibly pregnant. To end the Bisaan threat once and for all, the hunters set the mine on fire and burned the bodies.