Eddie was Marius, the one who fell in love with Cosette. I thought he was a terrific Marius (his "Empty Chairs at Empty Tables" is a killer), and I thought it helped that they moved Eponine's arc around from how it was in the stage version so he didn't seem as much of a dope.
In the show, Marius finds her dressed as a boy on the barricade, she tells him she did it to be with him, and he still sends her off with a note to Cosette.

She's the one who gives the letter to Valjean, and then she goes off and sings "On My Own".
In the movie, they kill her off before all that. Marius never knew she was there until after she'd been shot.
I love her song - and there's an opening to it that's missing in the movie, as well as a verse that's missing from her death scene.