Harvey hires a new secretary Gretchen Bodinski, who appears the opposite of Donna but proves herself capable. However, as capable as Gretchen is Harvey still struggles with losing Donna. After experiencing a serious panic attack, he seeks therapy but finds it difficult to open up to a therapist who wants to address his abandonment issues. She slowly gets him to talk about his mother's affair throughout the season. Meanwhile, Donna goes to Louis but Louis insecurity about Donna leaving him and returning to Harvey and it took a toll on their relationship, especially when he found out that Harvey pays Donna's extremely high salary out of his pocket because of his high compensation. As always Louis over reacted and conspired with partner Jack Soloff to change the firm's compensation structure and undermine Harvey, which gets him in trouble with Jessica as Soloff makes a power play. Jessica finds out that Soloff got advice from Daniel Hardman, and gives him one last chance at the firm. When Soloff tries to break ties with Hardman, though, the former managing partner finds ways to keep manipulating him.
Mike and Rachel got engage but decided to keep quiet about it as they work to help Harvey deal with Donna's departure. Mike works a case with Robert Zane; Rachel decides not to sign a prenup suggested by her father. Mike works a case where the opposing counsel is a former girlfriend who knows his secret, and Rachel is forced to handle the situation. Rachel is hurt by friction with her mother when Mike's secret forces her to give up her dream of a huge wedding. Hardman threatens a hostile takeover of Pearson Specter Litt, with Soloff as his involuntary right-hand man. Louis fails to discover what Hardman is holding over Soloff. Harvey realizes Charles Forstman, now in jail, is funding Hardman as an act of revenge, and Forstmann demands Harvey's resignation. When Hardman makes another move, Harvey agrees to resign and reveals the whole situation to the partners, leading them to vote to keep Jessica as managing partner. Mike also resigns after a difficult decision to protect his new family with Rachel but is arrested before he can leave the office by two agents who accuse him of conspiracy to commit fraud.
Season 5b come with the biggest question on all, will the team be able to get Mike free?