The wait is finally over for fans of “Castle.” The hit ABC series returns Monday with its Season 8 premiere and the new season will see some big career changes for Beckett (Stana Katic) and Castle (Nathan Fillion). Fans, though, may need a little refresher on what led up to the newlyweds new gigs at the end of Season 7.

In the Season 7 finale of "Castle," the case at hand was the murder of a woman who turned up dead in the woods with peculiar scars on her face. Castle recognized the scars from his his childhood. Thirty years prior, Castle had inadvertently witnessed a murder in the woods where the victim, another woman, was left with the same injuries. A flashback reveals that Castle had also seen the murderer -- a mysterious man in a black mask who told him never to tell anyone what he had seen. The traumatic incident was the reason Castle decided to become a mystery writer.

In the finale, he and new wife Beckett were on the hunt to put the killer away for good. The trail of clues eventually led to psychiatrist Dr. Holtzman (Wallace Langham). Castle recognized his voice from beneath the mask 30 years prior, leading to a tense standoff. At one point, Castle became cornered by Holtzman in a barn where the phsychatrist/serial killer was about to make Castle his next vicitm when a quick-thinking Beckett slid a gun under the barn door to her husband. Castle shot Holtzman and lived to fight (and write) another day. 

As for that cliffhanger, earlier in the episode while investigating the case, Beckett got called in to talk to a big wig at the police department (Lance Reddick) who chastised her for her often reckless methods and inappropriate relationship with Castle. Beckett did not back down, defending her police work and her marriage. It turned out it was all a game to test her resolve. Beckett was actually being vetted to possibly run for New York State Senate. Beckett told Castle, who said he would support her no matter what, but the episode ended with Beckett still up in the air.

Meanwhile, Castle ended the season a bit on the outs with the New York Police Department and in Season 8 he will have a new project to busy himself with in his non-writing time. The premiere synopsis reveals that he will be starting a private investigation firm and his first case will be finding his missing wife!

Will Beckett run for State Senate? Fans will have to wait to find out. The Season 8 premiere of "Castle" airs Monday, Sept. 21 at 10 p.m. EDT on ABC. However, impatient fans can spoil the cliffhanger for themselves HERE

Watch the promo for "Castle" Season 8 below: