During their training to become monster agents Nelly and Valle have been told that gnomes and goblins only exist in people's imaginations. In this adventure they have the opportunity to find out whether this is true. Nelly and Valle visit Valle's great grandfather Gunnar who lives in the home, an attractive house with a beautiful garden and stimulating activities provided every day for its old folk residents. But Nelly and Valle have hardly set their foot inside the home before they notice that not all is quite as it should be. The garden is becoming overgrown, dishes are piling up in the kitchen, there is cobwebs at the windows and the manager of the home seems tired and irritable. And worst of all, the residents just sit and sleep in their armchairs for the short time they are up in the day. Even Gunnar who was always so alert. Is all this because of the gnomes? It is said that they are behind all the thefts of all the round things that keep disappearing. Or is there someone else who is the cause of all this unhappiness? Nelly and Valle realize that they must investigate each and every part of the house to discover if there are small folk underground and what the manager is really up to.