There's a possum in our house....

There's a possum in our house and it's been hiding in the roof...
For a few weeks now the boys have heard these scratching sounds in the walls of their bedroom and over their beds at night and in the morning. At first we thought it may be a rat and set some traps. But when it continued, after a bit more scouting around we discovered it was a baby possum that was going up the inside of the wall cavity and sleeping in the roof during the day, then leaving again at night. And also fighting with our cat Ginger over who was boss of the garage:)
We tried blocking off a access to the garage, but that meant blocking ginger's cat flap, and we were never sure when the possum was out or in. And we didn't want it to get stuck and end up dying in the roof :(
At the moment we are renovating the kids bathroom and Jason was under the house working on some pipes when he spotted the possum trying to get into the wall, he managed to grab it by its tail and popped it into the old bird cage and has now taken it for a long drive to some bush that is no where near us!