The last time we saw Gary Cole on Suits portraying the role of Cameron Dennis was on season one. On the episode "Rules of The Game", he was introduced as Harvey's old mentor from the DA's office. However, things hit a snag between the two when Harvey was threatened for disbarment if he doesn't testify against his mentor.
When the legal drama returns for a third stab this summer in July 16th, don't be surprised if you see another feud building up between Harvey and Dennis. A spoiler came up and it suggests that the The Good Wife actor is returning for perhaps another villainous-gig on the well-watched cable series.
Here's a photo snippet taken by a fan:
Source: dietpunkfics @ Tumblr