Owen Cheats on Cristina
The abortion created a rift in Owen and Cristina's relationship. Owen so wanted to be a father and was hurt when Cristina took that away from him. They were fighting on and off for some time after when Owen was presented the opportunity to emotionally hurt Cristina. He was drinking in the local bar when a sexy woman struck up a conversation with him. One thing led to another and Owen ended up sleeping with her. He wasn't looking for a new relationship or even a good time, he was looking for revenge.