Maybe, just maybe, distilling the Civil War to good guys versus bad guys misses the point.

PBS’s Mercy Street continues to raise that possibility in its second season, Sunday at 8 p.m. ET (check local listings).

“It’s easy to reduce the Civil War to Union good, Confederates bad,” says executive producer David Zabel. “We’re looking for ways to balance the characters. We want them all to have shades.”

Mercy Street is set in Alexandria, Va., in the early days of the Civil War. Its focal point is the Mansion House Hospital, a large home that has been repurposed as a medical treatment facility.

While it’s run by the Union, its location ensures that people from both sides will have to find ways to live and work together.

Zabel points to one of the central characters, Mary Phinney (Mary Elizabeth Winstead, top), a nurse who arrives from Boston as a staunch abolitionist.

“Mary is a heroic character in many ways,” says Zabel. “But she has a prickly side. When she arrives, she doesn’t want to treat Confederate soldiers. That’s not how a nurse should behave.”

One of Mary’s fellow nurses, Anne Hastings (Tara Summers, right), has impeccable professional credentials, including battlefield work with Florence Nightingale in the Crimean War. She often seems cold, with personal ambitions that lead her to undercut those she feels stand in her way.

“She sometimes comes across as evil,” says Summers. “But she’s not. She’s fighting for what she believes in.

“She is jealous of Mary’s position. But this season we’ll see that she also has affection for Mary. A different side of her will come out. We will see her vulnerabilities.”

The Green family, whose palatial residence has been turned into Mansion House Hospital, incorporates a range of views. No one is disloyal to the South, including patriarch James Green (Gary Cole), but parents and children respond in several different ways to the presence of the Yankees.

Meanwhile, some of the occupiers try to be courteous, and others are swaggering bullies.

To no one’s surprise, black folks often get hammered from both sides.

Samuel Diggs (McKinley Belcher III, top) is a free black man who has desperately needed medical skills. But Union officers and doctors almost unanimously refuse to let him even help.

Further down the ladder, it gets worse. Mercy Street hasn’t reached the Emancipation Proclamation yet, but already there’s a dangerous limbo into which both slaves and some free blacks are falling.

“The story of black people often doesn’t get shown,” says Zabel. “Are they slaves or not slaves? They certainly aren’t treated with respect.”

Diggs is part of a substantial black population on Mercy Street, and one immediate impact of the new war is that it has put the scent of freedom in the air.

While that doesn’t mean the black characters all act in admirable ways, Zabel notes that they also haven’t been treated admirably.

What’s also different about Mercy Street, Zabel suggests, is that much of the story focuses on the viewpoint of the nurses, including Phinney and Hastings.

Besides reflecting the reality that most medical care comes from nurses, not doctors, he says, “We’re telling a Civil War story from a female point of view. You don’t see what very often.”

Zabel, who may be best known for his work on NBC’s long-running ER, says helping shape Mercy Street with co-creator Lisa Wolfinger was full of delights for him.

“Originally Lisa was working on a docudrama about medical advances in the Civil War,” he notes. “Then PBS came to us and asked if it could be a series. They said they had a lot of great British shows, so how about a great American show?”

He likes working with PBS, he jokes, because “PBS doesn’t live in as much fear as corporate entities.”

More concretely, he says, “It’s huge that you have no commercials, so you don’t have to write to breaks. It’s liberating. It frees you up to follow the natural pace of the story.”

The second season of Mercy Street, like the first, will run six episodes, which may seem short, but Zabel says works fine.

“There’s no lull,” he says. “Every episode has to be jam-packed. And as we move into the second season and get to know the actors, the characters will start to shape the show.”

Its mission of telling a different Civil War story will remain the same, he says, but he and Wolfinger also don’t want to turn Mercy Street into a lecture.

“Our goal is to make an entertaining television show,” he says. “We will not be gratuitously educational.”

“What I like,” says Summers, “is that the show doesn’t demonize either side. The characters are all standing up for something they believe in.”