Spend the summer by the sea? These holidays can be unforgettable! This is what Winnie, Cecilia and Henry think when their parents send them to stay with their grandparents. But the guys are in for a surprise: it looks like the residents of the dilapidated lilac house are hiding something. Many rooms are locked, and if you put your hand on the door on the second floor, you can get burned. Was there a secret pizzeria there? In addition, Henry's little brother swears that there is a magical forest on the second floor. And the strange trio of house helpers assures us that living here is very dangerous! Will the guys be able to unravel the secrets kept by the inhabitants of this house?