Consider this...
Driving home late one night, you're traveling through a semi-rural area. You pass houses occasionally; but for the most part it's just you, the mumbling of late night radio, and the trees. It's been ages since you stopped at that 7/11 to grab a cup of coffee and take a leak. You can feel that uncomfortable build-up and you know you got to go again.
You pull off at the first wide gravel patch you see on the shoulder. You jump out of the car, engine running, headlights on. As you relieve yourself into the edge of the woods, your mind begins to wander.
You think back to times when you and your buddies would take late night walks around your neighborhood. Any time you'd notice a car coming up behind you, you'd all jump into the woods. The car would pass, the driver completely unaware that a group of rowdy, likely drunk teenagers were merely feet away as they drove by.
The thought suddenly occurs that the same could be said for you now. That just a little ways into the tree line, past the light bleed of your headlights, could be a group of drunk teens laughing to themselves. Or maybe a group of sober teens, getting ready to jump you and steal your car. Or maybe something entirely different, watching you for completely unknowable reasons.
You finish, zip up and hop into your car a little quicker than you'd like to admit. You pull back onto the road quickly and soon the creeping fear begins to fade away, as some pop hit from your teen years comes on the radio, and you hum along. It's then that you notice it.
First it's just a blur out of the corner of your eye to the right. Probably an old sign post. Then you see it again a mile or two further on. Then again. This time you're on the look-out for it and you see it coming up on your right. It's as if something bought a cheap nude human costume and had it stretched over its bulbous form. You begin to panic as you find yourself lifting your foot from the gas pedal. The car slows and you can't help but turn your head to view it full on. You lock eyes with it... you're still driving.
You can tell you're getting close to home. A lot of time has passed—according to the dashboard clock—that you can't seem to account for. You're drenched in sweat and there's mud all over your shoes and pants, like you've been tramping through the woods. There's a wet stain on your passenger seat that smells foul. You pull into your driveway and jump out of your car. You dash into the house and lock the door behind you.
There are worse things that can happen.