Somewhere you live, a pebble crash landed on earth, and out came a tiny alien with tendrils, they burrowed into the nearest thing they could find which happened to be your pet dog that had being missing for a week. You dog is now on the brink of death and is being controlled. The alien takes it to your home. Your dog dies on your porch, the one alien had birthed many others inside the dog, all of the offspring fled to infect others. The main alien had stayed to infect you. You open the door, and you see it there, it charges at you.