Gwen Hernandez is a young woman that Sam and Dean helped after she and her boyfriend was attacked by Ramsey.
Background[]
Gwen was planning to leave for Washington to pursue her studies to become a veterinarian. Believing a long-distance relationship with Marcus wouldn't work out, especially since, while she cared for him she didn't love him, she convinced Marcus to go with her on a camping trip where she planned to end their relationship.
After Marcus left the camp to get firewood, Gwen found an engagement ring in his bag and sighed, knowing this was going to be much harder than she thought. However, she heard Marcus scream as he ran back to camp, telling her to run. He had an injured leg and was pushed down by something neither of them could see.
Ramsey attacking and killing Marcus infront of Gwen
To Gwen's horror, she watched Marcus die as something clawed fatal injuries into his back, and she could see paw prints forming in the mud as this invisible something approached her. In fright, Gwen struck the threat with an axe and ran. She called the police but they didn't believe her story that some invisible monster had killed Marcus.
Sam and Dean Winchester approached Gwen at her home, posing as FBI agents, where Sam told her Marcus was killed by a bear. Angry that no one believed her, Gwen told them to get out of her house. No sooner had they left however, the same monster that had killed Marcus attacked Gwen in her home and very nearly killed her. Luckily, Sam and Dean showed up and shot the monster, forcing it to run.
This time, Sam and Dean were honest with Gwen and told her this monster that had killed Marcus and was now after her was a Hellhound, an invisible monstrous dog from hell that hunts humans who sold their souls to demons. Gwen swore she never made such a deal and was certain neither had Marcus.
Crowley tells the Winchester brothers and Gwen that they are dealing with Ramsey
Dean then called on Crowley, who showed up at their location and informed them this particular hellhound was Ramsey, the oldest living hellhound and explained that hellhounds were created by God. But he found them too vicious and decided to have them put down. Lucifer however saved one of them, Ramsey, who was pregnant at the time, and so the hellhounds continued to exist.
Crowley then asked Gwen if she'd done anything to Ramsey, and she admitted she'd struck her with an axe, which explained why Ramsey was now after Gwen. The Winchesters asked if Crowley could order Ramsey to stand down but he said he couldn't because Ramsey is loyal only to Lucifer. He agreed to help them kill Ramsey to keep his own house in order.
The four of them returned to the forest where Gwen and Marcus went camping. Sam stayed with Gwen in the Impala while Dean and Crowley went looking for Ramsey and her den.
Sam and Gwen confronting Ramsey
As night fell, Gwen admitted to Sam her own guilt, believing that their situation and Marcus' death was all her fault, and how bad she felt that Marcus died just before he'd planned to propose when she had been planning to break up their relationship. But then Sam saw through his Hellhound Glasses that Ramsey was right in front of them. The beast attacked, damaging the Impala, and Sam stepped out to kill Ramsey, armed with an Angel Blade.
Ramsey knocked Sam down, making him lose his glasses so he couldn't see her. Right before she could kill him, Gwen stepped out and knocked Ramsey away with a bag, giving Sam the chance to take his blade and put Ramsey down.
With Ramsey dead and her life no longer in danger, Gwen thanked the brothers and even Crowley by giving him a hug, much to his discomfort. After Crowley left, Gwen commented "He seems nice".