[Warning: The following contains spoilers for Sunday's finale episode of The Outsider. Read at your own risk!]

HBO's supernatural crime drama The Outsider wrapped up its first season Sunday night with an episode that found Det. Ralph Anderson (Ben Mendelsohn) and private investigator Holly Gibney (Cynthia Erivo) having a final showdown with malevolent entity El Cuco. It tied the story up in a way that could serve as a series finale. And the Stephen King novel upon which the show is based doesn't have a sequel. So this could be the end of The Outsider.

But it probably won't be.

In the waning moments of the finale, "Must/Can't," Ralph had some lines that set up possible continuing adventures. "You know, I wouldn't mind teaming up again, if the opportunity ever arose," Ralph said. "Preferably something simple, like a gangland triple homicide, something like that." But it won't be something like that, because as Holly was walking out of Ralph's house to head back to her home in Chicago, the formerly skeptical detective asked her "what else is out there?" She gave him a little smile and a shrug, then shut the door.

Then, in a mid-credits scene like something out of a Marvel move, Holly was washing her hands when she saw a vision of Jack Hoskins (Marc Menchaca), El Cuco's final possessed helper, in the mirror. When she turned around, he was gone. She touched the back of her neck to see if she had a wound like Jack's on the back of her neck — which would mean El Cuco had marked her as its helper — but there was nothing there. Then, as she sat at her computer reading an article about Terry Maitland (Jason Bateman) getting exonerated for the murder of Frankie Peterson, a scratch was visible on her arm, and a scratch means something different than a neck wound. She's not going to be El Cuco's familiar; El Cuco is going to take her form and kill again. Thus, the seeds of a story for Season 2 have been planted.

The Outsider Review: HBO's Stephen King Adaptation Is a Chilling Blend of Crime and Horror

The Outsider has performed well ratings-wise for HBO, steadily growing throughout the season in the 18-49 demographic and in total viewers. Its ratings are comparable to those of Watchmen, another ambiguously limited series which HBO would love to bring back for a second season but might not be able to. However, it should be much easier to do another season of The Outsider than Watchmen, whose creator admittedly does not have an idea for the what might come next. By contrast, showrunner Richard Price told Indiewire in January that he was already at work on a second season, saying, "It's like pulling a rabbit out of a glass hat — of course there will be another (if HBO wants one). There's no such thing as a series that, if it does well, they're not going to want a second season." Hey, ifHBO was able to do a second season of Big Little Lies, The Outsider Season 2 should be a piece of cake by comparison.

It's also worth noting here that HBO never described The Outsider as a limited series, either. The network kept the show's status kind of vague, leaving open the possibility of a single season or something closer to an anthology format. And while a second season has not been announced, Stephen King indicated that he might be on board with the prospect when he retweeted a novelist friend of his who said, "Great finale. But I don't think this is the end of The Outsider." So, stay tuned.

The Outsider is available to stream on HBO — add it via Amazon Prime.

Cynthia Erivo, <em>The Outsider</em>Cynthia Erivo, The Outsider