En underbar present

Thingumy and Bob finally decide to go back to Moominvalley for a visit. As usual they lug their - to them enormous suitcase along. Remembering the equally enormous ruby it used to contain Stinky takes the suitcase from them. On arrival at Moominhouse Thingumy and Bob are desolate, because the suitcase held a wonderful present they were going to give to the Moomins, in fact a present for which they had exchanged their ruby . Stinky finds the present both worthless and inedible, and Thingumy and Bob get it back. But it doesn't seem to do what was promised...