Los Gatos, California - Heartstopper has welcomed a new member of the gang as the TV adaptation introduces a fan-favorite character from the novels.

The secret's out!

On Monday, author and series creator Alice Oseman confirmed that actor Darragh Hand would be joining the cast for season 3, taking on the role of Michael Holden.

Though Michael has a rather small role in the Heartstopper graphic novels, he's a pivotal player in Solitaire, Oseman's 2014 debut novel that first introduced Nick, Charlie, and Tori.

"I was very nervous and excited to begin the search for our Michael! Michael is a quirky, eccentric optimist with a sunshine disposition, and it was a challenge to find someone who I felt truly channelled Michael from the books," Oseman wrote.

"But then Darragh came along and warmed our hearts, made us all laugh so much, and perfectly complimented Jenny Walser's Tori Spring."

Official news of Michael's inclusion in the TV adaptation has sparked new theories among fans about which storylines would be making their way into season 3, as it likely signals a more expansive plotline than what is featured in the graphic novels.

Season 2 of Heartstopper, which debuted in August, adapted the third volume of the graphic novel series, with additional scenes pulled from Volume 4.

With the casting of Michael, it now appears certain that the adaptation will expand the plotlines of supporting characters by drawing on Oseman's prose novels — particularly Solitaire and This Winter, both of which primarily follow Tori and Charlie Spring.

Season 3's apparent inclusion of storylines well into Volume 5 of the graphic novels, as spilled by photos snapped from recent filming, has sparked fan concern about it being the show's final season, though no such decision has been confirmed by Netflix.

Filming of season 3 is still underway and is currently expected to wrap on December 20, per What's on Netflix.

Next month will also mark the print debut of the penultimate Heartstopper Volume 5, which is set to hit bookstores on December 19.