Robin was a waitress Sam encountered while travelling through his memories.
Robin met Sam when he stumbled into her bar with no memory. At first she thought he was a criminal, but after some begging from Sam, she put her weapon down. She asked for Sam's name but he didn't remember. She asked what happened, and Sam told her the police found him on a bench and he beat them up. Robin attempted to take Sam to a hospital, but he refused. Sam then collapsed, which worried her. Sam asked if she had a computer and he found the motel he was staying at. Robin asked if Sam was a hooker (he denied it), so she offered to take Sam to the motel.
They arrived at the Nite Owl and she followed Sam to the room he thought he was in. Sam asked her for her credit card, and she handed it to him. Sam used it to open the door and she asked who he was. Robin then commented on the news clips Sam had on his walls. Robin also began to ramble on and told Sam it is what she does when she's nervous. She also found all the fake IDs. Then Sam remembered his name and found a location that could help him. Robin at first, didn't really want to go that far, until they got shot at by an unknown shooter.
The two survived the attack however, so Sam drove Robin towards Sioux Falls, South Dakota in order to meet Bobby. Suddenly, he noticed someone in the woods nearby and urged Robin to stay behind. Whom Sam encountered was his soulless version, the shooter, and after a struggle, he won a battle against him, causing all his memories of his time as soulless to return.This led Sam to finally figure out who Robin was. Robin was a girl he killed when he was Soulless. He shot her when a Crossroad Demon was holding her hostage so the demon wouldn't have any leverage. Sam apologized to Robin for killing her. Robin responded by saying he shouldn't have dug deeper, adding that he's "not as sorry as he's gonna be."