The penultimate episode of "Suits" Season 3 is titled, "Know When to Fold 'Em." The preview of the episode suggests that the episode 15 of "Suits" is an episode "that changes everything." In the episode, Mike is likely to make a decision whether he wants to continue being a lawyer at Pearson & Specter, or take-up the new job offer in the field of investment banking.
In the previous episode of "Suits" Season 3, "Heartburn," Jonathan Sidwell, an investment banker, offered Mike an opportunity to play in the major league of investment banking. Mike had come-up with a legal as well as a business solution to help Jonathan quit Tony Gionopoulos' company, without facing a lawsuit for breaking the employment contract.
In the preview clip, Mike can be seen telling Harvey about the job offer, and Harvey telling Mike that if it was him, he would take it. Mike accepting Jonathan's job offer means, he quits being a lawyer. However as a lawyer, he will be stuck at the same position, as he never went to a law school. Also, there is always the risk of someone exposing his fraud.
The preview clip indicates that Rachel wants Mike to take-up the job, as there is always the fear of him getting caught. Harvey does not say it, but he needs Mike, as Donna can be seen telling Mike in the preview clip. It will be a difficult decision for Mike to make. Mike does not want to live a life feeling stuck and in fear, but he loves law and working with Harvey. It looks implausible that he will quit Pearson & Specter.
Meanwhile, the episode also features a former name partner, Charles Van Dyke. He will return to the firm, with revenge on his mind. The Hollywood Reporter had reported in October 2013 that Jamey Sheridan has been roped-in to play one of the original name partners, and his character has "an ax to grind." It was revealed in one of the episodes that Jessica and Hardman took over Dyke's firm, after ousting him. At the time, Pearson & Specter was called Gordon Schmidt Van Dyke.
Official Synopsis of "Suits" Season 3 Episode 15 "Know When to Fold 'Em": "A persistent attorney goes after one of Harvey's clients; Mike is faced with a difficult decision; former name partner Charles Van Dyke returns with revenge on his mind."