My son is almost 4 years old. He’s gone almost all four years of his life without really being scared of anything.

As a toddler, he used to climb over the couch onto a bordering saucer toy and then onto a nearby table- something like you might see in a dangerous high-wire-type circus act- without any fear at all.

My son has approached pit bulls without being afraid. He actually scares the dogs.

Halloween’s scary monsters have had little effect on the boy. He approached one particular monster last Halloween with the question, “Are you happy?” My son was worried that the monster was unhappy with his snarling “attack” face on.

But just as my son is about to turn 4, he found out what it is to be scared. The other night he woke from his sleep, got out of bed and came to his mom and me and told us that he feared a cow would open his bedroom door and come in and scare him. I’m not sure where that comes from. He hasn’t been watching any killer cow movies. And my “Far Side” cartoon books depicting sometimes scary cows are not within his reach.

For the past few days, my son has gotten out of bed and said he heard a noise.

“Is that the cow?” he asks.

I didn’t hear any noises. My wife didn’t hear any noises. My son most likely just heard the house settling. Ah, how I remember being afraid of house-settling noises as a kid.

My parents divorced when my siblings and I were young. But we were old enough to stay home by ourselves without a baby sitter. So when my mom began dating again, us kids stayed home, which was fun until nightfall. Once the sun tucked beneath the horizon, monsters and burglars combed our street in search of our backyard.

I have an older sister. She was “in charge” when my mom was gone. I also have a younger brother. He and I were ninjas. So when we heard the house settling- or any noises for that matter- my sister thought someone was in the backyard, she got on the phone to 911, and my brother and I dressed in our ninja gear and ran to the kitchen to arm ourselves with kitchen knives.

I preferred the Ginsu knife since it had been advertised on TV cutting through a penny. I figured it was the best weapon against burglars or any monster. (By the way: I don’t recommend any of these tactics to youngsters today. As far as you kids know, this is all a fairy tale.)

So here’s the typical evening with us kids at home alone: Mom’s off on her date. My sister jumps on the phone with her boyfriend, and my brother and I record another hilarious “Funny Dudes” program on our Fisher-Price tape recorder.

Nightfall hits. My sister is only just beginning her phone call with her boyfriend, even though it’s two hours since she actually began the call. My brother and I switch gears to playing our Halloween sound effects records. (We were those true monster lovers, until the monsters entered our backyard.)

Without fail, sister’s off the phone and upstairs in the bedroom my brother and I shared. And she’s on the cordless phone dialing the police. We knew what had happened. She heard a monster or a burglar in the backyard. She’s so frightened that she ended her important phone call with her boyfriend six hours too early. It’s serious.

My brother and I turn off all the lights in the house, strap on our black ninja outfits and rush over to the window to look out into the backyard. It’s dark out there. Any of those shadows back there could be from trees or worse . . . monsters.

My brother and I go through a serious debate: Do we go downstairs to the kitchen and get the knives and risk that the monsters or burglars already gained entry into the house? Or do we stay upstairs where it’s safer and find some other kind of weapon?

No other weapon would do. I needed that Ginsu knife. It could cut through a penny, after all. So I tell my brother I’d take the lead down the steps. But he must watch my back. The monsters could pop out at any time.

Slowly, we take the stairwell one step at a time, never skipping a step like we’d typically do during the day. Before we hit the stairwell, my brother and I temporarily arm ourselves with squirt bottles containing our own homemade “toxic potions,” which were usually a mixture of my sister’s bathroom products- and most likely toxic. (Again, this activity isn’t advisable.)

Armed with the squirt bottles, we reach the ground floor of our house. My brother and I concur that we both have itchy trigger fingers. My trigger is squeezed so that bits of potion are dripping off the nozzle and bleaching my ninja outfit and, worse, the brown carpet down the hall. (I figured I’d have to deal with that later. My brother and I had knives to obtain and monsters to slay.)

We make it to the kitchen. I quickly go for the Ginsu knife; my brother grabs a couple of other knives. Only later would I find out that he grabbed butter knives.

My brother and I hear a noise at the door. We run upstairs as fast as we can (please, kids, don’t run with knives) and slide underneath our beds. We pass my sister who is on her way to meet the cops at the front door. Yes, the noise my brother and I heard came from the cops on our porch. The coast was clear. No monsters. No burglars. Just the house settling.

And so now that my son has frightful visions of a deadly cow entering his room with plans to terrorize him, I’ve packed up all the squirt bottles and all the bathroom chemicals, and I’ve locked the kitchen knives in a safe. And my wife and I have vowed never to leave him at home alone- ever.

E-mail Michael Picarella at REUPHOLSTERY