"The X-Files" miniseries has been filled with laughs, scares, twists, monsters and moments that can bring a tear to your eye. One episode remains of the Fox revival series and it will be the most challenging and shocking yet for Mulder (David Duchovny) and Scully (Gillian Anderson). The two will try to save the country from a plague in episode 6, titled "My Struggle II."

According to the synopsis, a disease starts to spread around the country and people get "gravely ill." While many start to panic, Scully will look "within to find a cure," while Mulder will go to the man he believes to be responsible for it all. However, it could be someone else from their past that could end up saving the day.

The promo video shows Mulder coming face-to-face with the Cigarette Smoking Man (William B. Davis). Mulder wants Cigarette Smoking Man to stop what he put in motion, but Cigarette Smoking Man tells him "It's far too late for that."

The X-Files Finale Synopsis Mulder (David Duchovny) and Scully (Gillian Anderson) look to find a cure to an illness that's spreading across the country in "The X-Files" miniseries finale. Photo: Fox

The finale will be a continuation of episode 1, "My Struggle," where it was revealed that some sort of shadow government has been using alien technology to experiment on humans. Conspiracy theorist Tad O’Malley (Joel McHale) will be back, as will Mulder and Scully's new FBI allies Agent Miller (Robbie Amell) and Agent Einstein (Lauren Ambrose).

O'Malley teases the end of humanity, letting the world know that alien DNA is inside of "every American citizen," and Einstein is shown very sick. The promo video teases that the truth will finally be revealed on the show. The video comes to an end with an alien ship flying over a bridge. Will Mulder and Scully be able to stop Cigarette Smoking Man? Could the person from the past that could save everyone be their long lost son William?

You can watch the episode 6 promo video below:

"The X-Files" miniseries concludes Monday, Feb. 22, at 8 p.m. EST on Fox.