There's a new mystery waiting to be solved by criminal lawyer Annalise Keating and her students when How to Get Away with Murder Season 3 returns to ABC.

Show creator Peter Nowalk hints that the new mystery is bound to blow the viewers' minds and is set to make the already complicated lives of the characters even more twisted.

"There's going to be a new mystery and you're not going to have to wait long to find out what that is. The first domino was Lila getting killed, so it all stems from there. A leads to B leads to C, and I think we're probably at D at this point and it's going to be the biggest one yet, he promised.

For her part, actress Viola Davis, who plays Annalise, said that the mystery is so complex that even the cast couldn't figure out what they were in for even if they already have the script.

"We have been sitting on set, all of us, in different groups, and just talking about the mystery that's going to be revealed. We cannot figure it out! Last year we could figure it out, especially Alfie Enoch. They are just highly intelligent kids. But this year, cannot figure it out!" she said.

Like in previous seasons, the next big question that will run through the entire season will be revealed in the first episode and it seems that this time around, the stakes are higher as it may "cost everyone everything."

And it seems that the show is really bringing in the heat for the upcoming season as it signed on NYPD Blue alum Esai Morales and Grey's Anatomy guest star Amy Madigan, reported TVLine.

Madigan previously played a shrink in Greys Anatomy while Morales played the captain in NYPD Blue. While they have been confirmed to join the cast, their roles are yet to be revealed.

The report also indicated that Dexter alum Luna Velez is set to play the headmistress of the university that Annalise teaches in.

The show returns to ABC on September 22.