When Jonah and Katherine travel to early 1900s Switzerland and Serbia to return Albert Einstein's daughter, Lieserl, to history, her mother Mileva grasps entirely too much about time travel and has no intention of letting her daughter go.

Twelve-year-old Isabel dreams of seeing the world but has never left Oregon, and so when her best friend, Sophie, tells her of a baking contest whose winners travel to New York City, she eagerly enters despite concerns about her mother, who is opening a cupcake bakery. Includes recipes.

Percy, expelled from six schools for being unable to control his temper, learns the truth from his mother that his father is the Greek god Poseidon, and is sent to Camp Half Blood where he is befriended by a satyr and the demigod daughter of Athena who join him in a journey to the Underworld to retrieve Zeus's lightning bolt and prevent a catastrophic war.