A is someone who changes bodies everyday and she can't do anything about it. Since A changes bodies she doesn't think she has a purpose in life, so throughout the book A needs to find her purpose.
A meets Rhiannon while she is in the body of Justin, Rhiannon's boyfriend. While A is in Justin's bodies, she learns that he doesn't treat Rhiannon very well and she ends up falling in Love with Rhiannon.
"There are more people like you and me."
A and Rhiannon run away to Rhiannon's uncles cabin. since A can't stay over night because the persons body she was in for that day would wake up in a bed with Rhiannon, she goes home. But she promises Rhiannon she will be back the next day.
After Rhiannon got home from the cabin she wakes up in the body of Dana, who is hungover and did some bad things the night before. She is grounded and unable to see Rhiannon or even email her because it got taken away. Rhiannon gets really mad at A for leaving her there waiting all day and she begins to realize that they won't work out.
A meets Reverend Poole who is someone just like her and he tells her that there are even more people like her. He also tells her that there is a way for her to stay in one body for more than one day and maybe even forever. This gets A thinking that her and Rhiannon could work but she doesn't want to just take peoples lives from them.
A is in the body of Alexander Lin, he is a great guy who treats his family well, his girlfriend, and he has a great personality. A thought about taking his life to stay in forever but she knows that she can't so she meets with Rhiannon and they "start over" so they re met and spent a whole day together. Then A tells Rhiannon that they can't work but her and Alexander can, and the love will still be the same. The next day A gets up and runs so she can start her life again and leave Rhiannon behind.