Due to our recent sightings of a mouse in our home (

) we recently got a moggy as the mice were getting the food from the traps we put down but not getting trapped!?
Anyway he is an indoor cat and has been a bit spoilt by his previous owner.As far as we know he is about 9 months old.He was fine the first couple of days but this morning since we got up his been manically running around the lounge and kitchen as if he is hunting/trying to catch something (which isnt there)....my question is...is this normal for an indoor cat???
Is it because he is not releasing his energy by going outside?
How can i calm him down a bit when he does go mad?
Im asking because its a bit scary for my Jack and his been scratched by the cat (although it didnt leave a mark).