Ticktock - Dean R. Koontz

When Tommy Phan discovers a mysterious rag doll on his doorstep one day, he's curious but tries to dismiss it. However, the thing seems ominously foreboding - a feeling borne out when he hears a sound from it that evening. When he picks up the doll, its heart actually appears to be beating. Then the threads of its eyes unravel, and a strange green eye appears - and blinks.

Before long, Tommy is forced to flee an adversary that becomes larger, ever more formidable and seemingly indestructible. He must use his journalist's skills to figure out not only exactly what this thing is and where it has come from, but more importantly why it has been sent after him. And he has just nine hours before the arrival of dawn to do so...