Despite his nature and preference for conventional spy tactics, Casey has realized that Operation Bartowski is most effective with Sarah Walker, and omitted most of the details of Chuck and Sarah's emotional involvement from his reports to Beckman until she specifically ordered him to give an unabridged report. This led to a 49-B, a practice wherein another Agent (in this case, Agent Forrest) would assess whether or not the emotions between the two were a liability, which, eventually, Agent Forrest decided they were. While Casey admired Forrest's thinking, he also realized she was a greater liability on the team than Sarah, despite (or perhaps even due to) her feelings for Chuck. In a rare display of emotion, he told Agent Forrest that Sarah was the best partner he ever had and strongly disagreed with her assessment of her as a liability to the operation. He encouraged Chuck to tell General Beckman why Sarah should remain on the team. Casey and Sarah's relationship continues to grow, and Casey's strong bond with the whole team is displayed again at the end of Season 2. In season 3, Sarah stands up for Casey and helps him rescue his ex-fiancee and daughter when his old superior blackmailed Casey. Both Sarah and Chuck try to keep Casey on the team when General Backman fires him for "betraying" his country. In "Chuck Versus the Final Exam," Casey helps Chuck pass his Red Test by killing the mole (Perry) Chuck was meant to kill but couldn't. Sarah sees the dead mole and Chuck with a gun in his hand and assumes Chuck was the one who pulled the trigger. Because of that, she refuses to get back together with Chuck because she thinks he is a changed person. Later, Casey arrives at Sarah's apartment to find her packing, admits he was the one who killed Perry and Chuck was unable to pull the trigger. At this confession, Sarah's face lights up, and she thanks Casey, who responds with wishing her a good life as he departs. Casey's confession ultimately helps Sarah and Chuck get back together. In seasons 4 and 5, Casey and Sarah already refer to each other as friends and not just partners. They continue to work together and help each other when needed. Sarah even starts going to Casey for relationship advice. In season 4, they both acknowledge their priorities change, and they both begin putting family and friends first. In season 5, Sarah helps Casey with his love interest, Gertrude Verbanski, giving him advice and helping him ask her out on a date.