'American Horror Story: Apocalypse': Everything You Need to Know About 'Murder House'

Tonight's episode of American Horror Story: Apocalypse is taking fans back to where everything began in the eagerly anticipated "Return to Murder House" crossover episode. But as it's been seven years and a lot of twists and turns since the first season of the FX horror anthology series, even the most devoted of fans might just need a refresher on the Harmon family, the infamous Murder House, and just why Michael Langdon is so creepy.

The first season of the series, Murder House introduced fans to the Harmon family. Dr. Ben Harmon (Dylan McDermott), along with his wife Vivien (Connie Britton) and their daughter Violet (Taissa Farmiga) moved into the house looking for a fresh start after Ben had an affair and Vivien a devastating miscarriage. However, the fresh start wasn't all the family hoped it would be. Early on, Vivien is impregnated after being raped by the Rubber Man -- Vivien initially thinks it's Ben in a bondage suit -- and their restored mansion ends up being less of a dream home and more of a nightmare.

The Harmons have to deal right off the bat with their intrusive neighbor, Constance Langdon (Jessica Lange), as well some other curious characters including a previous homeowner who set fire to his entire family, and one of Ben's patients, a disturbed young man named Tate (Evan Peters). Things are further complicated when Ben's mistress, Hayden (Kate Mara) shows up pregnant with his child but is soon after murdered, the ghosts of previous owners start appearing the truth about things starts to unravel. Tate is Tate Langdon and he's a ghost, having been shot to death by the SWAT team after he killed 15 of his classmates in a 1994 school shooting. It's also revealed that he was the Rubber Man -- making him the father of one of Vivien's twins.

That twin? It's quickly learned that he's growing faster than the other and, in the season's penultimate episode, Vivien ends up having the babies at only around six months into her pregnancy. Vivien dies giving birth to them, it's revealed that Violet died in a previous suicide attempt, the smaller twin dies after taking one breath, but Constance manages to take the surviving child -- Tate's son -- after Ben is murdered by the ghost of Hayden. In the end, the entire Harmon family is reunited in death remaining in the house as ghosts determined to prevent the horrific deaths of future residents of the house by scaring them away.

As for the surviving twin? Constance takes the boy, named Michael Langdon, and in the last moments of the season finale the child is shown, three years later, greeting Constance with a smile, a trail of blood leading to where the boy has murdered his nanny. Of course, Constance doesn't appear to be surprised. After all, the medium Billie Dean Howard (Sarah Paulson) had told her that a child conceived by a human woman and a ghostly father would end up being the Antichrist and would bring about the end of days.

Considering that a now surprisingly grown Michael is doing exactly that, it makes sense that Cordelia (Sarah Paulson) would want to go back to Murder House and find out everything she can about Michael's history. For fans, the return will do more than just shed light on who Michael is now but will also see many favorite characters return. The McDermott, Britton, Farmiga, Lange, and Peters are all set to return as their Murder House characters in the episode.

Are you looking forward to tonight's Murder House crossover? Let us know your thoughts in the comments below.

American Horror Story: Apocalypse airs Wednesdays at 10/9c on FX.