Newly installed cat door works too well

[Catherine]

People decided to have a cat flap installed so their cat could come and go on its own. They had a handyman install the door.
He sent a video to show tat the door works. A cat can clearly be seen entering the house through the door. The only problem is that 
 it is not their cat!

https://www.boredpanda.com/handyman-installs-cat-door/

They are lucky that they only had one unknown cat enter their home. They set up an open door policy. They are lucky they didn't find a whole set of cats lounging around their home. Cats are smart. They could figure out how to come and go while the people are out and never be seen.

I wonder if their cat will use the door?