First-person narrator Harriet Wermer was looking forward to her summer, but there's a surprise change in plans: her mother, pregnant with the baby sibling no one asked Harriet if she wanted, has to be on bed rest, so Harriet's dad is taking her to Marble Island, where his mom lives. Harriet - and her cat Matzo Ball - will stay with Nanu and help run the B&B, whether she wants to or not.

Harriet is justifiably upset about this change in plans, equal parts mad and sad - but mad is easier. Crabby Harriet doesn't always treat those around her with kindness, and she sometimes lies, but she becomes intrigued by a key she finds cleaning out her Nanu's shed, and is determined to find out what it opens.

A story of acceptance, curiosity, and growth, with a flawed but lovable protagonist, an interesting setting (Marble Island is off the coast of California), and a minor subplot about birds and how one of their major predators is housecats.

Quotes

I don't understand; weren't grown-ups kids, before they were grown-ups? Do they all get, like, grown-up amnesia or something? (4)

A key that doesn't have a lock to open is a pretty sad thing, if you ask me. (138)

It seemed that every mystery I solved led to even bigger mysteries. (163)

"...sometimes, a key fits more than one lock." (Mable Marble, 186)

Why is it sometimes so much easier to say things that aren't true than to say things that are true, that are the most true? (191)

None of this was what I thought my summer would be like.....Yet here I was.
I could be mad about it. Or maybe I could be curious instead. (195) ( )

When her mom is put on bed rest for the remainder of her pregnancy, Harriet is sent to spend the summer at her grandmother’s bed and breakfast. Though stroppy about the change in plans at first, she soon becomes interested in exploring her surroundings, and finding the keyhole that fits the mysterious key she uncovers.

Meh, I was not in the mood for this kid today. She’s realistically flawed, but I was just not there for the compulsive lying. The pacing also seemed off; draggy at first and then rushed at the end. Actual kids might like this more than I did. ( )