Outlander episode 11 titled The Devil's Mark, airs on 18 April. The episode promises to reveal what's in store for Claire and Geillis who stand trial for witchcraft. Will the duo face a death sentence? The episode will also reveal a major secret about Geillis.

The upcoming episode's official synopsis reads, "Claire and Geillis stand trial for witchcraft; Claire learns a secret about Geillis' past as Jamie attempts a rescue."

A promo for Outlander's episode 11, shows the two women being locked up in an underground cell. They face trial in court where Claire cries, "You're all murderers". A spectator shouts, "Burn the witch!" Viewers will have to wait if the court has indeed ruled a death sentence as punishment.

What is Geillis' big secret?

According to a People report, a sneak peek video for the upcoming episode features a conversation between Claire and Geillis which teases the latter's mysterious character.

"They say I'm a witch," Geillis says in the promo video. (via The Christian Post)

"Are you?" Claire asks.

"I believe there are powers beyond what we can see and hear and touch," Geillis cryptically answers.

According to a VC Post source, the secret could be about Geillis' capability of time travelling. She confides this to Claire saying she can go to the year 1968.

In last week's episode Claire witnessed her friend dancing nearly naked in a ritual similar to what she and Frank witnessed in the 1940s. Immediately after the ritual Geillis reveals to Claire that she is pregnant with Dougal MacKenzie's child and that the dance was a "summoning" so that she can be with Dougal.

Talking about her role, actress Lotte Verbeek recently told E! News, "For my character particularly, Geillis, she's going to be really surprising. You're going to see a side of her you haven't seen before. Things are going to heat up quite a bit."

Outlander season 1 episode 11 The Devil's Mark, airs on 18 April at 9pm EST on Starz.

Click here or here to watch the episode live stream online.