Some roles are fun, some are physically challenging, and some get in your head from day one. That’s the case for Katie Holmes and company in the new movie "Touched with Fire."

Two manic depressives meet in a mental hospital, and all the volatility you’d expect quickly follows.

Katie Holmes plays Carla and Luke Kirby plays Marco, two extremely tormented souls who are also extremely talented poets.

Katie Holmes: "It was incredibly challenging to take on this character."

And watching them get caught between the extreme highs and lows of mania and depression — their helpless parents.

Christine Lahti: "It was intense in a great way."

Bruce Altman and Christine Lahti play Carla’s parents, who try everything from committing them to a hospital to hovering over them at home.

And just like Carla and Marco, these were incredibly demanding roles.

Christine Lahti: "I went home every day completely exhausted."

Katie Holmes: "It was kinda musical in a way."

"Touched with Fire" is based on a true story, but Katie says they were able to put their own stamp on it.

Katie Holmes: "We had a lot of improvs."

Luke Kirby: "Yeah, there was kinda a looseness to it."

"Touched with Fire" is now playing in theaters.

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