Auzou Indigo project book

Cosmo's dad went missing a year ago at sea. Since then, the boy and his best friend Liane have embarked on Project Indigo: to find out what really happened to his dad, or even to track him down alive... all while keeping it a secret from his family, who are getting ready to pay tribute to him without even knowing the truth. At the same time, strange things are happening in the house: his grandfather has been acting suspiciously since he reconnected with his old magician partner. The two of them refuse to explain what happened in Las Vegas, where Cosmo's grandfather claims to have lived for the past few years. Could they be up to something shady?