Inquisitive, passionate, inventive and funny – that’s 13-year-old Henni from Stella Street in Melbourne. Last Easter, when Henni was staying in a curious old timber house in Cauldron Bay, she found a box of old German books under the house. She decided to borrow one, and left a note in its place: ‘If you are related to Leopold Schmidt who lived here in 1915, please write to me.’ Imagine her surprise when she receives a postcard from Berlin from a LEO Schmidt! Although not what she expected, Henni begins to email ping pong with Leo which starts an email friendship and eventually leads to Leo helping Henni unravel the secret of Leopold Schmidt.
Leo is 13 years old and lives in Berlin, Germany. Leo has never met anyone from ‘down under’ but he swears he is not thinking that Henni lives upside down, feet on the ground, head dangling in the air. Leo is crazy about soccer and he’s a keen goalkeeper, but someone taller comes along and takes his place in the team. It was Leo’s Uncle Sascha who found Henni’s note. Sascha was filming a documentary about surfing and he always brings something back for Leo from his travels. Leo tells Henni about what’s going on in his life: some money is stolen from his desk, a bad scene at school, and then his friend Felix gets into trouble, and Henni is the only one Leo can trust with their secret.
Felix has been Leo’s good friend since elementary school. He loves riddles and knows a hundred of them, testing them out on Henni whenever he gets a chance. He’s also a great chess player and always has a bit of gossip to share. Although Felix was born in Germany, sometimes he’s treated badly because he is black. When Felix's mother becomes unemployed, Felix finds out that he and his mother are going to be deported to Namibia. Felix’s mother is put in detention while the police try to find where Felix is hiding. Leo is the only one who knows where he is, and Felix makes him swear not to tell anyone.
Maik goes to school with Leo and Felix. He’s a bit of a troublemaker but also the class clown. Often, he gets thrown out of class and his foster parents need to be called to school. He's a bit of a mystery to Felix and Leo and they can never guess what he's up to or whether to trust him or not.
Danielle is Henni’s nosey little sister. Future tennis champion, she is always hitting balls against the walls, or windows, or getting in the way. And she’s sneaky, slipping in an email to Leo that nearly scares Leo off his computer: ‘You are Henni’s boyfriend.’ But she adds spice to the family, and there are tennis balls all over Baker’s Hill, thanks to Danielle.