On the edge of your seat - Idioms by The Free Dictionary
on the edge of your seat
on the edge of (one's) seat
Excited, nervous, or filled with suspense while one waits to see what happens next. It's not going to win any Oscars, but the film certainly kept us on the edge of our seats from start to finish. Her character is so deliciously sinister and conniving that I was always on the edge of my seat to see what she would do next.
on the edge of your seat (or chair) very excited and giving your full attention to something. informal
on the ˌedge of your ˈseat/ˈchair very excited and giving your full attention to something: The film was so exciting it had me on the edge of my seat right until the last moment.