The mob-connected plot to break the legs of a deadbeat suburban businessman started at a dingy used car dealership in Melrose Park, federal prosecutors say.

Michael “Mickey” Davis, a longtime associate of reputed Outfit bosses Peter and John DiFronzo, walked into R.J. Serpico’s office, closed the door behind him and threw a piece of paper onto the desk.

On the sheet were scribbled notes from a mob bookie indicating Serpico’s father owed thousands of dollars in gambling debts. Serpico, who had taken a $300,000 loan from Davis to start the fledgling Ideal Motors dealership with his father, knew instantly he was in trouble.

“This wasn’t our (expletive) agreement,” Davis growled, according to Serpico’s recent testimony in federal court. “I want my (expletive) money.”

He then pulled up a chair, leaned in close and issued what prosecutors allege was a thinly veiled threat.

“How are your wife and kids doing? Are you still living in Park Ridge?” the hefty suburban landfill owner allegedly asked Serpico. “Does your wife still own that salon in Schaumburg?”

Without another word, Davis got up and walked out.

Prosecutors allege that within months of that ominous January 2013 confrontation, Davis, infuriated that Serpico had still failed to pay back the loan, ordered his brutal beating, enlisting the help of a well-known Italian restaurant owner in Burr Ridge to find the right guys for the job. The restaurateur went to reputed mob associate Paulie Carparelli, who in turn hired a team of bone-cracking goons to carry out the beating for $10,000, according to prosecutors.

Unbeknownst to everyone involved, however, the beefy union bodyguard tasked with coordinating the assault had been nabbed months earlier in an unrelated extortion plot and was secretly cooperating with the FBI. In July 2013, agents swooped in to stop the beating before it was carried out, court records show.

For the past two weeks, Davis’ trial on extortion charges at the Dirksen U.S. Courthouse has featured some of the biggest names in the depleted ranks of the Chicago Outfit, including the DiFronzo brothers and Salvatore “Solly D” DeLaurentis, all reputed leaders of the notorious Elmwood Park crew.

While none of the aging bosses has been charged with any wrongdoing, their names and photos have been shown to jurors as evidence of the 58-year-old Davis’ purported connections to the highest levels of the mob.

Serpico testified he was well aware of Davis’ friendship with the DiFronzo brothers and that he often saw Davis and Peter DiFronzo cruising past Ideal Motors in DiFronzo’s black Cadillac Escalade. He said he also had heard Davis was partnered with DeLaurentis, a feared capo convicted in the 1990s of racketeering conspiracy in connection with a violent gambling crew run by Ernest Rocco Infelice.

Davis’ attorneys, meanwhile, have denied he has anything to do with the mob. Davis has known the DiFronzos since childhood and has maintained a longtime business relationship with them through his landfill in suburban Plainfield, where two DiFronzo-owned construction companies have paid millions of dollars to dump asphalt and other construction debris, according to his lawyers.

To bolster their point that he had nothing to hide, Davis’ attorneys showed the jury a photo that Davis kept in his office at the E.F. Heil landfill. The undated photo showed a tanned Davis deep-sea fishing off Costa Rica with Peter DiFronzo, the shirtless mob boss appearing to be reeling in a catch with a pole harness strapped around his waist.

Jurors deliberated about seven hours Friday without reaching a verdict. U.S. District Judge Samuel Der-Yeghiayan told the panel to return Monday morning to resume discussions.

In his closing argument Thursday, Thomas Anthony Durkin, Davis’ attorney, urged jurors not to get swept up in the dramatic talk of gangsters and to focus instead on the evidence that Durkin said failed to connect Davis to the mob or any extortion plot.

“If you want to get swayed by looking at ‘murderer’s row’ here, Pete DiFronzo, John DiFronzo, Solly DeLaurentis, all the boys, then we are in trouble,” Durkin told the jury in his closing argument as the mobsters’ photos were flashed on an overhead screen.

Durkin also painted Serpico as a liar and called the government’s undercover informant, George Brown, “just pathetic.”

Both Carparelli and Brown have pleaded guilty to charges unrelated to Davis’ case and are awaiting sentencing.

According to court records and testimony at the trial, Davis, who often golfed with Serpico’s father, Joe, loaned the father-son team $300,000 in 2012 to purchase used vehicles to sell at Ideal Motors. The agreement called for the loan to be paid back within three years, plus an extra $300 per car sold tacked on as interest. According to prosecutors, Davis expected to more than double his money. But the deal quickly soured as the business floundered and Serpico’s father continued to gamble with the borrowed funds, court records show. By the end of that year, Ideal Motors was in trouble, with creditors breathing down the owners’ necks and cars being repossessed.

Serpico, 44, who is married with two children, testified he was terrified and sick to his stomach after Davis threatened him and his family at the meeting at Ideal Motors. He kicked his father off the lot to appease Davis, who became co-owner. Serpico also paid Davis nearly $60,000 in cash and a used Chevelle to try to buy some time, according to prosecutors.

Wracked with fear and not knowing what to do, Serpico “literally walked off the lot” that May 2013 and left control of the business to Davis, Assistant U.S. Attorney Heather McShain said in her closing argument. But with Ideal Motors a financial bust, Davis had had enough, McShain said.

“Mickey Davis made a decision to not only continue to collect but to follow up on his threat,” McShain said.

Over the next several weeks, FBI agents secretly recorded a series of phone calls and meetings between Carparelli and Brown in which they discussed the logistics of the beating, including concerns over whether they had the proper clearance from the Outfit to carry out such an attack in the DiFronzos’ territory.

In a recorded call on July 11, 2013, Carparelli told Brown their plan was safe because Davis had a direct line to the bosses, court records show.

“OK, listen, I met this guy (Davis) yesterday. You know who this guy is?” a transcript of the call quoted Carparelli as saying. “This is Solly D’s partner. Ok? …So, listen, we definitely can’t (expletive) around with these guys or we’re going to have a big (expletive) headache, a big headache.”

But Carparelli also saw the job as a chance to prove themselves to the bosses, saying if the beating was successful it would “put us right on the map, believe me when I tell ya,” according to the transcript.

A few days later, Carparelli told Brown his guys should approach Serpico as he left his new job as a salesman at Al Piemonte Ford, stage a fender-bender and attack him when he got out of his car.

“Say we give him a little tap, like an accident. ‘Oh man, I’m sorry,'” Carparelli said on the call. “Guy gets out of his car. Boom, boom, boom. That’s it.”