Eva Coupeau was the girl who saved Chuck Bass when he was shot in Prague at the end of Season 3 trying to protect his engagement ring for Blair. In Belles de Jour, when Chuck wakes up, Eva asks for his name and he replies "Henry Prince". Eva takes Chuck, who she believes to be Henry Prince, back to Paris with her.
In Double Identity, Chuck is adjusting to his new life in Paris with Eva. He accidentally runs into Blair while taking a walk. Chuck asks Eva to join him to get away from Paris so he could get away from Blair. Chuck had his bags packed, a new passport and a new identity as Henry Prince. However, Blair rushes to Chuck and saves him from leaving his old life behind. Chuck asks Eva to return with him to New York and reveals his true identity.
In The Undergraduates, Eva's influence on Chuck has made him a new man. He decides to introduce her to his family at Fashion's Night Out. Although Lily has forgiven Chuck for his past mistakes, Rufus still hasn't forgiven him for taking Jenny's virginity. Eric also hasn't forgiven Chuck for attempting to rape Jenny when she was fourteen and reveals it to Rufus. Eva felt nervous about meeting Chuck's family because she felt she wouldn't be able to fit in. To make matters worse, she runs into Blair at a boutique where Blair puts her down and makes her feel insecure. At Fashion's Night Out, Eva overhears Chuck and Rufus's argument and leaves when Chuck denies her as his new girlfriend. He chases after her right before she stepped in
to a limo. Chuck apologizes and tells her he is ashamed of his history with women as well as revealing that to her. Blair witnesses their kiss with a sad expression on her face.
In Touch of Eva, Chuck gives Eva an expensive watch and Blair becomes jealous of their relationship. Blair goes to the store where the watch was purchased and witnesses Eva returning the watch. Blair shows the video she took of it to Chuck. Eva explained to them that she used the money to help Chucks valet, Ivan, so he wouldn't be kicked out of his own home. Eva felt she wanted to help Ivan since she was new to the city and he was kind to her. Chuck decides to donate five million dollars to a charity and he asks Eva to pick which charity to donate to. Blair spends time with Eva to find out about her past in order to take her down. Eva reveals that she grew up on a goat farm where her family were cheese makers. She dropped out of nursing school to help her family pay for the bills. Eva said she heard a gunfire outside of her apartment in Prague and rushed outside to see what is was. She nursed Chuck back to health when she saw no ambulance arriving. Dan, Serena and Blair discover that Eva was a prostitute. When Chuck finds out and confronts Eva, they reconcile despite the fact and he pretends that he has known all along.
Lily still had Chuck's items that were found on his person when he was shot because she constantly forgot to return then to him. She couldn't find Chuck so instead she gives them to Ivan instead. Chuck decided he was going to donate the five million dollars to a new charity dedicated to Eva. Blair tells Chuck that Eva knew who Chuck was before they met as she took his passport. Chuck searches through Eva's belongings and finds his passport. When he sees Eva, he tells her to leave. Lily asks Chuck if his belongings have returned to him safely yet. Chuck questions her about it and Lily lists the items that were in the envelope, including his passport. Chuck discovered that Blair took the passport from the envelope, put it in Eva's suitcase and made up the story about Eva knowing Chuck's identity. Chuck rushes to Eva to apologize and begs for her to stay. But the damage had already been done. Chuck had believed Blair over Eva when Blair had been trying to break them up from the beginning. Eva leaves New York and returns to Paris.
Chuck confronts Blair and asks her if she was scheming because she hated him so much, she couldn't stand him being happy or if she still loved him. Blair said she never meant to chase Eva out of New York and that she would never forgive Chuck for what he did to her. Chuck tells her Eva made him a good man and Blair only brought out the worst in him. He declares war on her and leaves.
At the end of the episode, Ivan tells Chuck that Eva will be deeply missed and Chuck fires him, showing that he had already returned to his dark side.