An old friend resurfaces on Monday’s new episode of House.

But will he remain a friend of House’s after our favorite doctor discovers what this guy is up to and, most importantly, who he’s up to it with?

Mysterious, poorly-worded questions aside, though, the installment is titled “Known Unknowns.” check out the official Fox promo below, followed by a trio of images from “Known Unknowns.”

Watch new promo of House Season 6 Episode 4 - Instant Karma

Below are the 7 Sneak Peeks of House Season 6 for those that could not watch them from the FOX site.

The “House” season premiere coming up next week? So un-House like.

With all the series regulars besides Hugh Laurie — and Robert Sean Leonard, who appears as Wilson in one very short scene — absent from the two-hour episode which spans the several months that House spends in a mental facility, you’re either going to love what the writer-producers have done or you’re going to hate it.

And Cuddy fans who want to see Princeton-Plainsboro’s fearless leader together with the cranky doctor should beware.

As has been rumored, House is indeed hooking up with the character played by guest star Franka Potente… and its pretty serious.

Like so serious that our guy might shed a few tears because of it.

Uh, yeah.

Not to worry, however. According to executive producer David Shore, House — though he’ll certainly attempt to change — will end up being the same man he’s always been in the end.

I spoke with Shore, as well as Robert Sean Leonard, Lisa Edelstein and Peter Jacobsen, recently and they all weighed in on the situation.

Shore is also spilling on Foreteen’s current relationship, plus Cameron and Chase and how the two will figure back into the mainstream action this season…

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Following a guest-starring stint that received mixed reviews (and rumors of his own spin-off), Michael Weston will reprise his role on House this season as private eye Lucas Douglas.

Last fall, House hired Douglas - who turned out to be quite similar to the honest cranky doctor we all know and love - to trail around Wilson. He appeared in multiple episodes and then pretty much vanished.

But Michael Ausiello confirms Weston’s return to the series this season, though plot details are unknown at this time.

Meanwhile, Hugh Laurie told E! News that season six will also feature a lot of nudity. Seriously. Or not seriously. It’s hard to tell when he speaks in a British accent…