The season 2 finale of Mr Robot airs on Wednesday (21 September) at 10pm EST on the USA Network. Episode 12 is titled, eps2.9_pyth0n-pt2.p7z, where fans will finally learn about Phase 2 and Tyrell Wellick will reveal a big "final secret".

Click here to watch Mr Robot via live stream on the USA Network. You can also watch the episode online in the US by clicking here.

In the previous episode, Wellick made a surprise return and met Elliot inside a cab. After some initial reservations which ended up with the driver throwing them out of the cab, Tyrell said, "I know you're under a lot of stress. I'm under a lot of stress, too. Can you even begin to imagine what it's been like for me?"

"Enough of these games. Let's go. We're close." To which Elliott responded, "[Close] to what?"

"Have you forgotten everything?" Tyrell questioned him and said that The Dark Army has completed Stage 2 of the society's plan. "It worked, Elliot. It's up to us now." Episode 10 ended with Tyrell repeating the final line of Casablanca, "Louie, I think this is the beginning of a beautiful friendship."

A promo for the episode shows Tyrell leading Elliot into an abandoned warehouse as the former E Corp employee asks, "You really don't remember this, do you?"

The promo then notes, "The final episode... the final secret... the wait is over." And then sweeping shots of Tyrell and Elliot's intense moments are seen as E Corp trucks are parked in the background with some men unloading boxes onto a street. The video ends with Mr Robot, Elliot and Tyrell looking at something as Wellick declares, "Are you ready to look at what we have accomplished?"

Martin Wallström who plays Tyrell in the hacker drama spoke to The Hollywood Reporter about his character's surprise return and what fans can expect going ahead. When asked about Tyrell's story in season 2, the actor said, "We have conversations about character and what's coming. I kind of knew the overall arc, but what I feel is so great is that even when we shot season one, sometimes we wouldn't know what was going to happen in the next episode."

The 33-year-old continued, "You have to play the scenes anyway, not knowing what's coming. I think that's the beauty of this show. You just lean back and enjoy the ride, and trust that whatever's going to happen is going to happen. Not knowing too much in advance, sometimes, is a blessing. At least it is for me. It makes me very relaxed, feeling that I'm a part of this, and let's just go for this ride."

Wallström also teased a lot of surprises in the finale episode and revealed, "To be honest, I'm always surprised, and never surprised. These writers are so good. They're very, very good. You just trust in what they're doing. I always expect to be surprised."