I’m not crazy, doctor. There really is a cat in my wall.

A Brooklyn man found himself locked up in a loony bin for four days after he smashed down walls in three apartments trying to rescue a fugitive feline.

The bizarre tale began when a mischievous kitty named Rumi decided to explore a hole in the wall of a condo undergoing renovation in Carroll Gardens.

Unfortunately for Rumi, the hole opened on a 30-foot shaft and he fell to the bottom.

The contractor, Chris Muth, had been watching Rumi for a friend and panicked when he went missing.

He couldn’t reach the cat from that apartment – even after enlarging the hole.

So the super, Doug Steiner, got him permission to make a small hole in the wall of another unit.

But, Steiner said, “He opened up all the walls. I said, ‘What the hell are you doing? The owner’s going to flip out.’ ”

Muth couldn’t catch Rumi from that hole either, so he broke into a third apartment, and again started smashing walls.

Steiner had as much success coaxing Muth out as Muth did with Rumi.

So the super called cops – who shipped Muth to a local psych ward.

Rumi remained in the catacombs of the condo – a former church. And the shrinks decided Muth was suffering from bats in his belfry.

The hospital records say he had a “bizarre delusion [he] was trying to save a cat of his friend,” The Brooklyn Paper reported.

But it all ended happily.

Muth finally convinced the doctors that he wasn’t a wacko.

And Rumi, tired of his 15 days in solitary, let himself be caught by professional cat rescuers using a fishing-pole-like device.

“After 60 hours stuck down there, I thought the cat was going to die,” Muth told The Brooklyn Paper.

“Otherwise I wouldn’t have panicked like I did.

“I can fix holes, but I can’t bring a cat back to life.”

leonard.greene@nypost.com