Jemima Rooper has promised a "darker", "more adult" second series of Atlantis.
Rooper confirmed to Digital Spy that she will reappear as Medusa late in series two's run.
"I enter around episode eight," she revealed. "You're going to see a short but hard burst of her this series."
The actress added that viewers will see "a good progression" from the first series, which aired on BBC One in late 2013.
"It seems to be that it's taking a more adult turn, and it's getting darker," she teased. "All the stakes are bigger."
Series two of Atlantis has been filming in Wales since earlier this year.
What to Read Next
Jemima Rooper currently stars in Breeders at the St James Theatre in London's West End until October 4.
Atlantis: What do you want from a second series?
Watch Jemima Rooper in a clip from the first series of Atlantis below:
