Auzou Books for my first investigations volume 5 the lake monster

Enzo is spending the holidays in treehouses with his parents and his dog Max. He meets other kids there: Zoé, Joachim, Gabriel, and his sister Manon. The boys, two teenagers, tell him that a monster lives in the lake and feeds on small animals, like little dogs. Enzo soon receives secret messages in Morse code sent by Zoé, who suggests he should be careful with Max. When his dog goes missing, Enzo starts investigating and questions Zoé before heading to the lake to find the famous monster. Will Enzo be fast enough to save his dog?