Fiona and Lucas have a secret. It isn't just any old secret but an enormous, gigantic, immense one: the F family (that is to say Fiona and Lucas's family) is part of a witness protection program. As a result of this they have to move house frequently (something that would normally be upsetting for two regular children). Making friends, unpacking suitcases, adapting to new places... all this upset every time the siblings start again, yet again, from zero. The problem is not doing anything that could cause them to be discovered. Will they be found? Who will mess things up this time?