the unknown shadow

In 1999, my family rent a house. Its beautiful house with big land besides. We lived there for 2 years. 

One day, it's just only me in the house. As usual, i took a nap 1st then i woke up. I opened up my room door and suddenly i saw a brief of shadow goes behind to kitchen. I chased it but not until 2 second, it's gone. I felt nothing and just switch on my tv.

But there is nights when we heard some foot-steps noise from upstairs.