Taylor Swift makes her series acting debut on "CSI: Crime Scene Investigation" -- and only ET is behind the scenes with the best-selling musical artist of 2008.

"I am obsessed with the show," she tells ET's Thea Andrews. "I have seen every episode every season."

What she didn't realize from watching is how hard it is to play a dead body!

"I've watched the show for so long, but in the beginning when you see the dead bodies you don't realize that those are people that are sitting really still and holding their breath and having their eyes in one direction, because they're so good at it," she exclaims.

Taylor plays Haley Jones, a young woman who has had three separate encounters over the years with Nick Stokes (George Eads), who has come to the motel where she lives as part of his job investigating crimes.

"The story is this girl is a victim of circumstances," says Taylor, who is wearing a brunette wig the day ET is on the set. "She has this lack of self-esteem, which is why she feels she needs to change into a different person to be loved."

So how is she doing?

"She is loving it," George tells Thea. "To be that young and successful musically, she must have followed her instincts. I keep telling her to do the same here."

Taylor's episode of "CSI" airs tonight at 9 p.m. on CBS.