Stranger Things: The First Shadow is turning Broadway upside down with its opening at New York’s Marquis Theatre on Tuesday, April 22. But one of the original stars of the Netflix horror series it’s based on was not among the attendees.

Millie Bobby Brown, who has played Eleven in Matt and Ross Duffer’s hit since its 2016 debut, is not joining the First Shadow premiere event. The actress, 21, is instead busy filming one of her next projects: Enola Holmes 3.

The star-studded list of guests supporting the team behind The First Shadow, which transferred from an acclaimed run in London’s West End, includes many of the Netflix series’ actors: Noah Schnapp, Natalia Dyer, Charlie Heaton, Jamie Campbell Bower, Cara Buono, Matthew Modine, Brett Gelman and Priah Ferguson.

Enola Holmes 2. Millie Bobby Brown as Enola Holmes.

Millie Bobby Brown in ‘Enola Holmes 2’. Alex Bailey/Netflix

Also not attending the event was original series actress Sadie Sink, who did visit a preview of The First Shadow on Monday. That was her day off from starring in director Danya Taymor and playwright Kimberly Belflower’s John Proctor Is the Villain just across the street at Broadway’s Booth Theatre.

Brown played the title character in 2020’s Enola Holmes, the story of Sherlock Holmes’ intrepid younger sister, and its 2022 sequel. In addition to that and the Stranger Things series, she has been busy in a variety of Netflix projects, including last year’s Damsel and The Electric State this March.

Enola Holmes 3 is bringing back Henry Cavill as Sherlock Holmes, Helena Bonham Carter as matriarch Eudoria Holmes, Himesh Patel as Dr. Watson, Sharon Duncan-Brewster as Mira Troy, Louis Partridge as Tewkesbury and more. Director Philip Barantini helms the sequel, which, like its predecessors, is adapted by Jack Thorne from Nancy Springer’s book series of the same name. Barantini and Thorne have collaborated before, on the Netflix hit Adolescence.

“Adventure chases detective Enola Holmes to Malta, where personal and professional dreams collide on a case more tangled and treacherous than any she has faced before,” reads an official synopsis.

First Look at Stranger Things TFS Broadway - Louis McCartney (Henry Creel), Marriott Marquis Theater

‘Stranger Things: The First Shadow’.Matthew Murphy and Evan Zimmerman/Netflix

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Thorne and the Duffer brothers are among the creatives behind The First Shadow, directed by Stephen Daldry and Justin Martin and written by Kate Trefry, who has worked on the Stranger Things TV series since its second season. The play is a prequel set in 1959 Hawkins, Ind., an origin story for high school-aged Jim Hopper, Joyce Maldonado and Bob Newby — the characters played on screen by David Harbour, Winona Ryder and Sean Astin — and Henry Creel (a.k.a. Stranger Things‘ Vecna).

“I was really given free rein to go crazy,” Trefry told PEOPLE of the play’s conception. “It [had] to fit in with everything we’ve done before on the show, and it also had to tie in with season 5, which I was working on at the same time that I was writing the play.”

Stranger Things season 5 is expected to premiere sometime in 2025. Tickets for Stranger Things: The First Shadow are on sale now.