The cast and crew of "Orphan Black" have been very quiet about the new season. Lead star Tatiana Maslany has also kept mum on the subject, only saying that season 4 will have a "new mystery" when it returns to BBC America. But now, more news has been pouring in for the critically acclaimed series, with co-creator John Fawcett taking to social media to let fans know that filming for the new season has begun.

Fawcett took to Twitter on Tuesday, Sept. 29, to post a picture of him with Maslany dressed as one of her characters—Helena—and actor Kristian Bruun. The co-creator wrote, "@OrphanBlack #CloneClub Yep we are rolling!"

BBC America has also released the official synopsis for the new season. According to the synopsis, Sarah, having returned home after hiding out in Iceland, is going to track down "an elusive and mysterious ally" who has a connection with Beth Childs. Sarah will take a cue from Beth and form a dangerous relationship with a powerful new enemy, which will head in a horrifying direction. As she strives to protect the sisterhood and keep everyone safe, Sarah's old habits begin to resurface.

When the show returns, viewers will get to see Felix (Jordan Gavaris), Mrs. S (Maria Doyle Kennedy), Art (Kevin Hanchard), Kira (Skyler Wexler), Scott (Josh Vokey), Ferdinand (James Frain), Kendall Malone (Allison Steadman), Susan Duncan (Rosemary Dunsmore), and Ari Millen as a mysterious new Castor clone.

A new face will also be seen in season 4. According to The Hollywood Reporter, "Rookie Blue" alum Joel Thomas Hynes has been added to the cast as a series regular and will play Dizzy, a hacker who refuses to conform to group mentality.

Season 4 will have 10 episodes and filming will reportedly continue through March 2016.

"Orphan Black" season 4 is slated to premiere in Spring 2016 on BBC America.