Some of the bravest acts are routinely performed on hands and knees while crawling in total blindness toward direst danger.

Any movie that sought to depict such an act of pure courage could only present a screen of impenetrable black.

So the demarcation between real life and make-believe could not have been clearer when FDNY Engine Company 69 responded on Thursday night to the report of a fire at a Harlem building where actor/director Ed Norton was filming Motherless Brooklyn.

Norton and his co-star Bruce Willis have become famous for their skill at portraying people other than themselves in ways that touch a range of emotions in millions of people, sometimes entrancing, other times frightening, other times amusing, in accordance with a script.

The firefighters of Engine 69 were exactly themselves as they stretched a line down into the reality of a smoke-charged basement, where the fire seems to have started. The universal law that heat rises once again forced brave men to proceed on hands and knees into a realm where they could not be seen, even by each other.

The first firefighter to crawl into the enveloping blackness, the literal leading man, was on the nozzle, 37-year-old Michael Davidson. The one on the nozzle actually directs the water onto the fire.

“Every firefighter wants the nozzle,” FDNY Commissioner Dan Nigro would later say. “Every firefighter wants that moment of battling a fire, of pushing it back, and feeling when ultimately you defeat it… saving life and property by literally fighting fire.”

Davidson had joined the FDNY two years after 9/11, when it lost 343 members. He had soon demonstrated the same spirit his fallen brothers had shown at the Twin Towers. His second year at the FDNY he had suffered serious burns to his hands, but he had stayed on the nozzle and kept advancing on what some call the Red Devil.

“ He would not stop. He kept fighting. It was clear from the very beginning of his career that he was special. ” — FDNY Commissioner Dan Nigro

“Mike pulled forward, crawling and inching, room to room,” Nigro would later say. “He would not stop. He kept fighting. It was clear from the very beginning of his career that he was special.”

Now in his 15th year on the job, Davidson had started off Thursday building a snowman with his four young children in the family’s front yard in suburban Floral Park. He had then headed in to work and here he was in Harlem, just before 11 p.m., as intensely and totally himself in the fire with his fellow firefighters as he had been in the snow with his kids. Daddy and nozzle man were a singular one.

In earlier times, before firefighters routinely used masks and air tanks, an engine company would go backward down into a basement fire and proceed until they could endure no more. Even a firefighter as powerful in body and spirit as Davidson would have been able to advance only so far.

But with a breathing apparatus consisting of a 45-minute air cylinder and a face mask, Davidson and the others were able to venture much farther. He and his comrades down in the movie set basement would never have run short of courage and determination, but the vibra-alerts on their cylinders signaled they were running low on air.

Engine 69 was relieved and began to withdraw as another company prepared to take its place. The usual away to leave in the total blackness is to follow the hose back out with your hands.

“That’s your lifeline,” a fire official would later say.

But a loop had formed in the hose and Davidson seems to have made an inadvertent u-turn, following the hose back in rather than out with the others. He ran out of air and pulled away his face mask.

Suddenly, Davidson could have been back the days before such equipment. But he was far deeper into danger than his predecessors could have gone. A few breaths of the poisonous smoke would have been enough to render him unconscious.

When his comrades got to Davidson, they discovered that this firefighter they had always thought of as invincible was beyond saving. He was pronounced dead at a Harlem hospital. A long line of firefighters stood outside to salute him as his body was brought out to be transported to the medical examiner’s office.

The wake was on Palm Sunday, the start of Holy Week. The funeral was on Tuesday at St. Patrick’s Cathedral. Thousands of firefighters gave a white-gloved salute as the engine that Davidson rode to his final fire rolled slowly down Fifth Avenue, polished to a gleam, new white lettering across the top of the windshield.

“In Loving Memory of FF Michael Davidson.”

Behind that came the rig of Ladder 28, which shares with Engine 69 the firehouse known as the Harlem Hilton. Then came the kilted Emerald Society Pipes and Drums, filling the air with the muffled rhythm of heartbreak.

Next was the ceremonial caisson, bearing the coffin, covered with an FDNY flag. The band fell silent as the caisson stopped just past the cathedral entrance, and the center of the City of New York was as hushed as a private prayer. The sky was clear and bright, but the street was in shadow and the air carried a chill that seemed to deepen as Davidson’s wife, Eileen, emerged from an FDNY van along with her children. They had last seen their daddy when they were building a snowman.

“Fatherless in Floral Park,” a family friend had said after the fire.

The uniformed pallbearers carried the coffin to the cathedral. The family and relatives and friends followed, along with as many firefighters as could fit inside.

“Jesus came to save us from everlasting flames,” Timothy Cardinal Dolan intoned. “Michael to rescue us from earthly ones.”

Mayor Bill de Blasio gave the first eulogy, declaring Davidson “a hero of the highest order.” Commissioner Nigro followed and spoke of that time when Davidson had kept advancing on the fire despite the burns on his hands.

“A natural born nozzle man,” Nigro said.

Nigro noted that Davidson was both the son and brother of firefighters. The brother, 34-year-old Erik, also delivered a eulogy. Erik said that in thinking of Michael he had decided that the best way to describe him was “salt of the earth.” Erik had looked up the definition and now read it aloud.

“An individual considered as representative of the best and noblest element of society.”

Erik added of Michael, “He was a man of high moral principles and ideals, and never wavered from that.”

Erik said it was only fitting for Michael’s funeral to be held at this cathedral and for grand Fifth Avenue to be shut down.

“Let the city and people of New York and the entire country say to themselves, ‘Wow, this guy must be important,’” Erik said, adding, “And still that would be the understatement of the century.”

He was exactly right, for Michael Davidson was a true star of the spirit and soul such as was seen at his home and firehouse every day, but only at that movie set when Engine 69 rolled up.

The brother made clear that Michael Davidson was ever ready to risk all to save the lives of others because he took such joy in living his own life, however tragically short it proved to be.

“When you think of Michael, please, please, please, I beg of you, laugh, don’t cry,” Erik said. “He wouldn’t want it any other way.”

The brother’s request was put to a test after the Mass ended and the coffin was carried back to the caisson. Eileen Davidson stood holding her 3-year-old, Emily, as a fire officer presented her with a helmet bearing the number 69.

Buglers played “Taps” and the NYPD did a helicopter flyover in the missing man formation. And while still nestled in her mother’s arms, little Emily raised her right hand. She waved in the direction of her father’s coffin.