The season 4 of "Suits" opened with Mike working as an investment banker in a different firm. The first episode also introduced Gillis' Industries takeover battle and opened the storyline of SEC investigation against Pearson & Specter. The episode eight of "Suits" Season 4 saw the return of Mike to his old firm. He immediately found himself working on a strategy to defeat Sean Cahill, the SEC investigator close to Harvey's nemesis, Eric Woodall.
Mike helped Harvey stall Cahill's attempt to get a search warrant against Pearson & Specter. He also came-up with the suggestion that they show all the files related to Gillis' Industries to Cahill, as they have nothing to hide. It is Mike who figured out that Louis is hiding something about his deal with Forstman.
In the new episode, Louis will confess to Harvey and Jessica that he made a huge mistake. The preview suggests that Jessica is not in a mood to forgive him, while Harvey can be seen accusing Louis of putting the firm in jeopardy because he wanted to be a hero. Louis screams that he had no choice. Louis failing to report about Forstman's tactics to evade taxes had its consequences. Forstman also made him a partner in his crime. The episode "Gone" will feature the unfolding of the consequences because of Louis's choice to impress Harvey.
It is Louis who ensured the return of Mike to Pearson & Specter. Also, Katrina in "Expsoure" told Mike what Louis gave-up to get him back in the firm. She said to Mike that Louis cared more about him than himself. The prodigal son may step-up to find a way out to save the firm and everyone. It, however, depends on what Louis plans to do next. The preview clip suggests that he is in a revolting mood.
According to official Synopsis of "Suits" Season 4 Episode 9 "Gone": "The SEC investigation comes to a head as Sean Cahill begins a round of depositions -- no one at Person Specter is safe, and no topic is off limits, as the inquisition unearths secrets both professional and personal."
At the end of episode 8, "Exposure," Mike realised that his love for Rachel is stronger than his hatred for Rachel's moment of weakness with Logan Sanders. Rachel and Mike are back together as a couple and they are likely to work together, closely, to help the firm come out of the mess, blemish-free. If Logan Sanders arrives as he is the key to the investigation, things may heat-up, again and get twisted.