Eileen Leahy was the only daughter of Padraic and Maura Leahy who lost her parents to a Banshee as a child and became a hunter for revenge. She was also a legacy as her grandfather was a Man of Letters.
In 1985 when Eileen was a baby, a Banshee broke into her home and attacked her father who had recently had a nervous breakdown due to losing his job. Eileen's mother was the daughter of a Man of Letters and knew some basic spells so she cast a banishing spell as the creature went after Eileen. The spell saved Eileen at the cost of her mother's life, but Eileen was rendered deaf from the Banshee's scream.
After her parents' deaths, Eileen was found by a hunter named Lillian O'Grady who had been hunting the Banshee. Lillian raised and trained Eileen to be a hunter before dying of cancer when Eileen was 16. Following her death, Eileen continued hunting the Banshee on her own for the next 14 years.
Eventually, Eileen tracked the Banshee to Oak Park Retirement Living in Lebanon, Kansas where the Banshee was feeding on the residents. Disguising herself as an employee named Marlene who was on vacation, Eileen investigated the two murders committed by the Banshee there and mistook Sam and Dean Winchester for two Banshees working together. Eileen trapped Sam who recognized her as a hunter and convinced her they were on the same side.
As Eileen bonded with Oak Park resident Mildred Baker, Sam realized that Mildred was likely the Banshee's next target due to a heart problem leaving her vulnerable and Mildred agreed to be their bait to lure the Banshee out. While preparing a spell to trap the Banshee, Sam and Eileen discussed revenge and Sam's own experience with it. Eileen showed uncertainty as to what she'd do once she got her revenge, telling Sam that while she didn't know her parents, they were still family.
That night, the Banshee attacked, but went after Dean rather than Mildred as was expected. As the Banshee was working on getting Dean to bash his head in, Eileen signaled Mildred to activate her spell. Mildred trapped the Banshee, allowing Eileen to kill it with a gold blade and get her revenge.
Following the death of the Banshee, Eileen told Sam that even though she got her revenge, her parents were still gone and killing the Banshee wouldn't bring them back. Rather than going on to a normal life, Eileen told Sam she was going to continue hunting as she was good at it and could help people. Sam invited her to drop by the Bunker sometime since she was a legacy and they joked about her deafness.
Powers and Abilities
- Spell Casting - Eileen was able to cast at least a powerful binding spell, having been taught by Lillian O'Grady.
- Expert Hunting Skills - Having been raised by a hunter, Eileen was a skilled hunter herself.