Last January, it was a dark cybernetic future that the Mad Horse Theatre Company portrayed in its production of “The Nether.” This year, the setting is in the past, but the darkness is still there. Poetic flourishes and a few laughs, however, help to lessen the gloom – a little.

Naomi Wallace’s award-winning “One Flea Spare” takes place in 17th-century London, where the bubonic plague is producing pits full of dead bodies while those hanging onto life are subject to a disintegrating social order.

The action is set in and around the home of a wealthy couple. When a sailor and a young girl, ostensibly trying to escape the pandemic, arrive uninvited, the now-quarantined foursome must cope with their dire situation.

Director Reba Short has taken advantage of the intimate, three-quarters-in-the-round performance space in South Portland to effectively contain the societal microcosm suggested by this complex and thought-provoking play. While a line of dialogue may occasionally be lost to one or another section of the audience as performers face away, the overall closeness fits the piece well.

Payne Ratner plays the wealthy William Snelgrave as a bit of a fop who touts his political connections while being essentially a prisoner in his own house. Vowing to mete out revenge when the siege is over, his bewigged patriarch reveals a nasty, snarling interior as the others slowly bind him to his misery.

Deborah Paley, as Darcy Snelgrave, perhaps the most sympathetic character, mourns her own circumstances while finding a source of cheer (and a bit more) in the presence of the home invaders. Paley convinces in showing that liberation comes at a price.

Mad Horse regular Nick Schroeder, as the rough-hewn sailor Bunce, provides an ominous, elemental presence that sets the Snelgraves on emotional fire. He gruffly dishes out tales of life at sea while becoming intimately acquainted with the repressed upper class onshore.

Gracie Brassard takes on the complex role of the mysterious young girl Morse, who deals numerous verbal blows to the adults’ increasingly threadbare identities. A veteran of local children’s theater productions, the 11-year-old Brassard skillfully embodies the strange, reckoning power behind her lines.

Mark Rubin rounds out the cast as the periodically appearing guard Kabe. Boisterous and bawdy, Rubin’s character entertains as a sort of sardonic jester, adding songs and silliness to bring home the bleakness of the situation.

The costumes by Christine Louise Marshall and set by Meg Anderson approximate the hierarchical prerogatives of the period, adding a touch of visual commentary to what is another trip, guided by Mad Horse Theatre, into the darkness.

Steve Feeney is a freelance writer who lives in Portland.