The Ogre Downstairs
is the story of three children who are unhappy about their mother's remarriage to a man they think of as the Ogre
and living under one roof with him and his two sons. Then the Ogre buys each set of children a chemistry set, which turns out to have bizarre and magical properties. When their experiments go wrong, they are forced to work together to reverse them and conceal the mess from their parents.
There are spoilers associated with this entry.