It was Christmas Eve 1856, and five slave families at the plantation in the Haymarket area had hatched a plan.

By all accounts, George Green, the plantation’s owner, was a cruel, unforgiving master, and he had let it slip that after a year of hard work, his slaves would not get their customary time off during the Christmas season.

Everyone, up to the oldest grandmother, helped plan Green’s murder, said Jimmy Pierce, the Prince William County historian who manages the Ben Lomond Plantation site. The plan was simple: They would kill him and burn down the house to cover up the crime.

Green was slain, but the plot was soon uncovered and the ringleaders were hanged after confessing.

It’s a grim tale for Christmastime. But it will be included in a holiday tour of the Ben Lomond Plantation that focuses on slave life, Pierce said, because it helps tell the story of Southern slaves at Christmas.

Rob Orrison, who manages Prince William’s historical sites, said Virginia’s historic places offer many holiday-themed events. The Ben Lomond site — a county-owned Colonial plantation that served as a Confederate hospital during the Civil War — is one of few in the region that includes preserved slave quarters.

The idea for a Christmas tour focusing on slavery was hatched when the county’s historians were brainstorming about how to incorporate Ben Lomond’s slave quarters into their holiday programs, Orrison said. Although very little is known about the slaves who lived on the Ben Lomond property, Orrison said, the county wanted to draw on stories from the surrounding area to give people a sense of what is known about slaves’ lives at Christmastime.

The Ben Lomond site hosted a daytime event last year, Orrison said, at which historical interpreters portraying slaves were on hand to tell stories and answer questions. After the success of that event, they decided to stage a more formal evening candlelight tour.

Although candlelight programs are common at historical sites around Christmas, Orrison said, “none of them talk about what the slaves did.” Because Ben Lomond includes the original slave quarters, “we thought this was a good opportunity.”

The tour will feature interpreters performing short vignettes, the George Green incident among them, Pierce said. Visitors will proceed through the house, and the tour will conclude in the slave quarters.

Slaves were sometimes given time off or a good meal at Christmas. But it was also a season of great anxiety. Because most slave owners were doing their year-end finances in December, some slaves would be rented to other plantations or sold outright. They could also be given away as gifts.

“It all really depended on the type of master you had,” Pierce said. “We’re trying to portray the hopes and the fears.”

The tour is 5-7 p.m. Saturday; tickets, $5. Ben Lomond Plantation, 10321 Sudley Manor Dr., Manassas. To make reservations (recommended), call 703-367-7872.