Mystery cat

Hi! I often find open the front door at 10 or 11pm at night to find a strange black cat sitting on the front step... It happened today...my birthday and also last year...after a close family member passed away the strange black cat was sitting on my door step at 10 or 11pm each night for almost a week!

When I step out the door it runs away into the night....what does this mean? I am baffled?!Cute cat too...no idea to where or to whom it belongs....