At the empty firm, Mike (with the hood of his sweatshirt up) is ready to go in and pee orange Gatorade all over Hardman's carpet, but Harvey keeps stopping the elevator and saying they need something more original. "I'm gonna get the can opener," he says with gravity. Mike is stunned that he might find out what happens with the can opener, and joins Harvey on the elevator. Whose doors close on us just as Harvey is saying, "What we do is--" Of course.
They're not alone at the firm, of course, even this late at night. Louis sneaks into Harvey's new office and sets about trying to guess his computer password. He spots Harvey and Mike before they spot him (while Mike is still confused about the purpose of the thumbtacks) and scurries to make himself look innocent. Of course Harvey isn't fooled when he comes in with Mike, and he pushes Louis up against the wall and draws back a fist. Mike stops him, yelling, "You hit him, they win." A terrified Louis scampers out of there. And now we'll never find what happens with the can opener.
After the ads, Mike is rifling through Harvey's record collection looking for something planted by Louis, like drugs. Which gives him the idea of doing the same thing to Hardman. Even while high, Harvey points out that's a crime, but Mike reminds him that Hardman would do the same to him. Harvey has an epiphany (the stoned kind being extra-visible, as it turns out), and wonders if maybe Hardman planted that damning memo from his old Coastal Motors case in the first place. You know, the one that caused so much trouble earlier in the season? Which would explain how Donna didn't remember seeing it. And now they're out at Donna's cubicle, where Mike has just finished fiddling with Donna's "received" stamp to show how easy it would be to backdate something. Plus there are no cameras or locks in the file room.