Mercy Tannen was the daughter of Goodman Tannen. She first encountered Marty McFly, going under the alias of "Martin", in 1692 during the Salem Witch Trials. Mercy was attracted to Marty, when he found out Goodman Tannen was her daughter. He knows Goodman Tannen would kill him, if he dates her or even talking to her. Marty broke it off. Mercy wanted get back at him, when her father ask her about Marty was talking to her about. Mercy lied and told him, that Marty was a witch and tried to come on to her. She found his actions were unworldly and that he was speaking in strange tongues, and agreed with the rest of the townsfolk that Marty was a witch. After Marty presumably drowned in the water test, Mercy felt remorse for what she did as she wanted to teach him a lesson for spurning her affection, not knowing that he was rescued by the browns and return back to 1991. She also looks like Liz, who was Marty and Jennifer's friend in college. Just like Mercy Tannen, she also had a crush on Marty.