It's been a month since Lennie's nineteen-year-old sister Bailey died, and Lennie is a mess. She refuses to move any of Bailey's things in their formerly-shared bedroom, she's writing poetry about Bailey and leaving it all over town, and she's barely talking to her best friend Sarah or the people she lives with, her Gram and Uncle Big. She's never known her mother, who supposedly has the family's "restless gene" and left when she was young—but she's even feeling her mom's absence more strongly now that Bailey's dead.
Oh, and since the funeral, she's been attracted to every boy.
But there are two boys in particular who are paying attention to her. There's the new boy in school, Joe, an excellent trumpet player with a beaming smile who wants to play a duet with her. Before you aw, though, we should mention that Lennie used to be a talented clarinetist, but for some mysterious reason, she all but quit. So she really doesn't want to play the clarinet.
Meanwhile, Bailey's fiancé, Toby, ends up kissing Lennie while they're talking about Bailey—not so much in a creepy way as in a desperate, sad sort of way. And Lennie kisses back.
Things heat up with both boys. Toby tells Lennie he and Bailey were secretly engaged. (Hang on—we swear we're getting to the "heating up" part.) This surprises (and kind of hurts) Lennie because Bailey hadn't told her. Plus, Bailey's childhood dream was to study acting at Juilliard, and though she got rejected, Lennie assumed she would try again. A wedding would've gotten in the way of Bailey's dream. With all this surprise and confusion in her head, Lennie thinks about the wedding Bailey might've had, and she and Toby both get really sad and start kissing again.
While she's dealing with the guilt of making out with Toby, summer hits and Joe starts coming over every morning. He makes friends with Gram and Uncle Big, and seems to temporarily lift their depression. Eventually, he tells Lennie he likes her and she actually tries playing her clarinet with him. After a face-plant the first time, she tries again and she feels a temporary sense of relief.
But even as she's falling for Joe, life is complicated. She finds her statue of St. Anthony, the patron saint of lost things, on Bailey's desk, and later learns that Bailey had been seriously searching for their mom before she died. Lennie's been trying to avoid Toby since she really likes Joe, but this discovery drives her to ask Toby why Bailey was searching. Toby tells Lennie that Bailey was pregnant, and that launches them into another grief make-out session. Joe shows up at that exact moment and storms off.
Suddenly alone, Lennie turns to Sarah for help getting Joe back, and apologizes for avoiding her. Sarah's bright idea is to seduce him with her looks, which (surprise) fails. Lennie finally packs up Bailey's things and takes them to the attic, where she finds a box of unsent letters Gram has written to her mother. The letters reveal details that she never knew about her mother, and these details make her mom seem real and her abandonment feel worse.
Then, to cap off her terrible week, Lennie sees Joe at the movies with someone else, so she cuts Gram's magical love roses and brings them to Joe's. It doesn't work, and Gram is furious about the roses. She tells Lennie that she's been selfish, that she's been grieving just as hard as Lennie is, and Lennie hasn't even talked to her.
This pushes Lennie to have a real conversation with Gram and ask about her mother. Gram finally tells her the whole story—that when her mom wanted to leave her kids with Gram, Gram threatened her by saying if she did that, she could never come back. Gram's guilt makes Lennie realize she's had a mother this whole time—Gram.
The ending is a happy-sad mix. Lennie writes a love poem to Joe, and it turns out Joe has read all the poems she's been scattering everywhere. They helped him understand her, and he forgives her. The last pages of the book feature both Uncle Big's wedding and a trip to Bailey's gravesite. At the gravesite, Lennie finds Bailey's engagement ring, and can't help thinking about how her sister doesn't have a future. She realizes grief never goes away; it is something she will always carry with her.