When Harvey Guillén first learned that his “What We Do in the Shadows” character, Guillermo, would finally be turning into a vampire, he thought the show was ending.

“They didn’t tell us that Guillermo was going to become a vampire until we had our meeting for the beginning of the year,” the actor recalls on a video call from Spain. “I thought we were going to wrap it, because where else do you go with his character?”

But it turns out the writers of the acclaimed vampire mockumentary did have more stories to tell. Among the storylines audiences will see in the sixth and final season of “What We Do in the Shadows,“ which launched last week and airs weekly on Mondays through Dec. 16, is Guillermo’s efforts to figure out what to do with his life now that he needs to move on from his lifelong dream of becoming a vampire. In the finale of Season 5, Nandor gives Guillermo a choice — become a vampire or return to being a human. He chooses to remain human, but it meant sacrificing Derek (Chris Sandiford), his friend and the vampire who turned him. (Derek is saved, though — he’s reanimated by the Necromancer (Benedict Wong) in exchange for the cash Guillermo paid Derek to turn him — minus $270 he spent on “vampire clothing” from Hot Topic.)

Paul Simms, showrunnner and executive producer of FX’s “What We Do in the Shadows.”

(Victoria Will / For The Times)

“A lot of what this season is about is his efforts to break away and start his own separate normal life and the vampires then following him to quote-unquote help him on his way in the real world,” says “Shadows” showrunner and executive producer Paul Simms. “We had a lot of heavy conversations in the writers room about things like that that had one on in our own personal lives. The underpinnings of it were real things that everyone feels at some point.”

The otherworldly comedy premiered in 2019 and has followed a group of vampires — Nandor (Kayvan Novak), Laszlo (Matt Berry), Nadja (Natasia Demetriou) and Colin Robinson (Mark Proksch) — and one time familiar Guillermo, who share a Staten Island home. (Guillermo has since moved out of the main house but remains on the property, in Laszlo’s garden shed, “where there is a smell — mildewy.”)

And aside from Guillermo’s efforts to find a real job, the final season will see Laszlo recommitting himself to a forgotten scientific pursuit — reanimating a human — Nadja sating more of her curiosity about humans, Colin seeking out companionship and Nandor possibly finding love where he least expected. According to Simms, the season is meant to be accessible to first-time viewers but features plenty of little details meant to satisfy those who’ve been along for the full ride.

While the showrunner remains tight-lipped about the finale, which, as usual, was written while they were filming the season, he describes it as “bittersweet” and calls it a “happy ending.”

“No one dies,” says Simms. “There’s a sense that life goes on.”

Showrunner Paul Simms, far right, is tight-lipped about the finale, saying only, “No one dies. There’s a sense that life goes on.”

(Victoria Will / For The Times)

Over the past five seasons, the series — which was based on Jemaine Clement and Taika Waititi‘s 2014 film of the same name — has created memorable storylines and characters, developing a vampiric universe that’s transcended the original material. Simms and the “Shadows” cast have been on a farewell tour this year — I spent a day with them at San Diego Comic-Con in July and interviewed them again earlier this month before their trip to New York Comic Con. The actors noted they’d been in touch with each other about how strange it felt to not be heading to Toronto to film this time of year. (Demetriou sat out the NYCC appearance after giving birth to her child.) As “Shadows” comes to a close, the actors and showrunner recount in their own words, edited for clarity and length, memorable moments and character arcs from the show.