In Sweet Tooth, Parker defends Maggie from her rude customer, and she is immediately attracted to him. Though, later on during the Halloween party, Lucy introduces Parker as her boyfriend.
In Exorcise Your Demons, Maggie has a conversation with Lucy about being on the verge of failing World Literature. Not wanting to "bring down Kappa's GPA", Lucy asks Parker to tutor Maggie, and he agrees. Later, Parker shows up to the same place where Maggie and her sisters are exorcising a demon from Angela Wu, claiming to "look for a place to hide fireworks". During this conversation Parker almost sees a possessed Angela, and to distract him Maggie quickly pulls him in and kisses him.
In Other Women, Lucy starts to suspect that Parker is cheating on her, so she asks Maggie to figure it out. Parker states that he wants her, not Lucy. So, Parker and Lucy ultimately break up.
In Out of Scythe, Maggie starts having romantic dreams with Parker. When she meets up with him, he notes that she has been avoiding him, Parker tells her that Lucy gave them an okay to date because she has already moved on. During this date, they have a deep conversation about "feeling like they aren't enough", especially compared to their family. They then start to kiss, when Maggie overhears Parker thinking that he does not want Maggie to find out the truth about him. This gets Maggie concerned. She starts investigating to figure out what Parker is hiding. She goes to the fraternity house and finds Parker injecting himself with a needle. She assumes that he is doing drugs and runs away. Later on, Parker comes to explain himself to Maggie. He says that he was taking medicine because of a rare autoimmune disease that he does not want people to find out about. Maggie concludes that is the secret Parker was keeping from her. They both share a passionate kiss.
In reality, Parker does not have an autoimmune disease. It is revealed that he is the shadow demon that The Charmed Ones had been trying to stop from stealing the Scythe of Tartarus.
Maggie's intentions with their relationship are pure, while Parker's may not be.
Parker knows that Maggie is a witch (and a Charmed One), and was assigned by his father to get close to Maggie.
As of Jingle Hell, Maggie knows of Parker's half-demon status.