James Marsden might be the world’s best secret keeper.

As Theodore “Teddy” Flood on Westworld, Marsden played a critical role in the first two seasons of the HBO series as the closest thing to an outright good guy a show this morally complex is capable of having. That is until, amid a robot revolution, his girlfriend Dolores (Evan Rachel Wood) reprogrammed his robot mind to strip him of his moral compass in service of the larger revolt. As a result, Teddy eventually reached a point in the series’ second season where he realized what Dolores had done to him and, as a result, committed suicide in front of Dolores out of grief. As such, Marsden exited Westworld accordingly—except he didn’t.

Instead, Westworld creators Lisa Joy and Jonathon Nolan told Marsden he’d return to the show later as a critical part of a new story arc they planned to tell. As such, Marsden had to lie to everyone around him for the better part of four years to keep his return under wraps. “With this show, you kind of have to put it under lock and key and forget about it and act as if you really are gone. Otherwise, you’ll trip up,” Marsden tells Complex. “I lied to my mother, brother, and sister that I wasn’t coming back. Mainly because—not that I don’t trust people that I’m close to—but I know how rapid these things can spread.” But it worked; a few weeks ahead of season four, Marsden’s involvement was officially announced by Joy and Nolan, much to the surprise of the Westworld faithful. 

The nature of Teddy’s return is one of season four’s biggest arcs—and for good reason. Turns out the charming cowboy is playing a critical role in the story of Wood’s new character named Christina. In this season’s fifth episode, viewers finally got more context around how and why Teddy was back, as he’s functioning as a way to help Christina discover some truths about the world in which she lives. But how and why Teddy knows what he knows remains to be seen.

As we inch closer to Westworld’s season finale, Complex spoke to Marsden over Zoom to talk about a wide range of topics, including how he found out about his return, working with Wood again, the challenges of working on such a mysterious show, and much more. Needless to say, spoilers for Westworld Season 4 are below.