Summer is for group shows in art galleries and innocent family fun on the beach. Right? Not on the second count, if you believe what “Nightmares of Summer,” a new group show at Marvelli Gallery, has to say.

“Nightmares of Summer” is co-curated by the somber duo of Marcello Marvelli and his collector friend George Robertson, whose previous collaborations include an investigation of suicide. They have gathered images that reflect “the darkness inherent in all paradigms of light, the dark cloud contained by every silver lining.” Rather than a gothic horror fest, however, this strange gathering is characterized by perverse good cheer.

Barnaby Furnas sets the tone with “Holiday” (2005), an angel of the apocalypse masquerading as a child on the beach. Mr. Furnas has made the terrifying exhilarations of battle his distinctive theme in images, often in watercolor, that at first read as joyous explosions of color, and only yield their awesome portents on closer examination. Here a young, fleshy beauty with golden wings wears a demented expression on her face and splatters what could be blood in all directions.

A second image by Mr. Furnas is a glowing red composition that looks a bit like a close-up of a molten oil rig. The image itself isn’t as sinister as the title, “Dead Red” (2005), and the medium: dispersed pigment in urethane and ink on bald calfskin.

This keeps company with a pair of nautical drawings by Francesca DiMattio of 19th-century battleships caught in distress.These crackle with a sense of danger that recalls David Fertig’s neo-Romantic Napoleonic battle scenes. Ms. DiMattio’s works in turn flank a dense, brooding charcoal drawing by Steve DiBenedetto, “Untitled (Situation With Octopus)” (1998-2004), in which the octopus looks like he is having a whale of a time.

Nils Karsten’s collages display a macabre sense of humor. Mr. Karsten gives spiky body hairs to the smooth legs of the appropriated little Victorian girls who populate his ghoulish untitled watercolor and collages of 2006.

In fact, a theme running through this show is the ickiness of sweaty limbs, parched throats, and exposed body parts. Diane Arbus’s “A Family One Evening at a Nudist Camp, PA”(1965) is an unconvincingly nonjudgmental view of an ill-at-ease, corpulent couple and their child under an ominous sky. The parts and prosthetic limbs in Hans Bellmer’s awkwardly thrust-together mannequin, “La Poupee” (1935) and the wacko elongations of Andre Kertesz’s “Distortion #28” (1933) – both vintage gelatin-silver prints – find echo in a pair of poignant collages by Robert Beck that focus on press photos of the naked corpse of a murder victim at a gay pickup beach.

Michael St. John brings an “In Cold Blood”-meets-the-Mansons sensibility to his nightmarish evocations of murder. One canvas, “Dead Body Inside” (2006), features the words of the title in a demented scrawl next to photograph of a forlorn cabin.

The poster girl of the last Whitney Biennial, Marilyn Minter, takes body squalor to Dantean depths in her blown-up C-print deconstructions of the beauty myth. “Soiled” (2000) has copious dirt between a cropped image of lurid, green-painted toenails, while “Drool” (2004) focuses on a menacing, saliva-filled mouth animated by a vampire-like grin.

Some of the remaining images qualify as nightmarish due to guilt by association. Ann Craven’s Hallmark-like portrait of two pink birds in a tree and Stuart Elster’s sickly monochromatic seascape at dawn become convincingly nightmarish just by keeping company with overt horrors.

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The pervasive misery in “Re: Location” is neither fantastic nor seasonal – it derives from the alienation and privation of exile and war. Some of these artists are overt in their politics and others are more oblique, but all convey a sense of frustration and fear.

Willie Doherty’s three sets of five Cprints, laminated on aluminum, come from his larger “Apparatus” (2005) series.They dwell on scenes of grim decay in Northern Ireland: boarded-up houses, tattered flags, graffitied projects. The “troubles” have been Mr. Doherty’s career theme. Somehow he finds hidden poetry in his hideous landscapes, creating constructivist patterns, for instance, in the way he crops a bird’s eye view of barricaded walkways.

Cages and barriers are often the Palestinian-born artist Mona Hatoum’s metaphor of choice for oppression, alienation, and exile. Her work here seems lighter at first: It is a curtain on which she has printed a newspaper article. The title, however, hints at political portend: “Every Door a Wall” (2003).

The visitor passes through this curtain to the back gallery, where an object by another artist of Palestinian-Arab extraction, Emily Jacir, gains added meaning from its placement. “Embrace” (2005) is a pointless luggage carousel, around 6 feet in diameter, with a motion sensor activated by the viewer. Is this a complex metaphor for exile and the frustrations of reconciliation?

The cool meanness of this object sits well with other exhibitors. Diango Hernandez’s “The Underdevelopment Is a Long Game, Do You Want To Play” (2005) has the words of the title in shiny little letters along a rusty pipe that is placed within an oval toy train track. Rita McBride’s inscrutable, 1970s-style architectural fixture, made of brass, is installed at ceiling level, its usage unspecified. Relief from such pretense and tedium comes in the form of an untitled, stainless-steel sculpture by Doris Salcedo, as ever poetic and enigmatic in her melancholy description of the human condition.

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If you prefer your nihilism with a smile, then head to James Cohan’s group show “A Brighter Day.”

This is sprawling show of 18 artists united in their chirpy interpretations of oppression, decay, and the apocalypse. Several artists bombard the viewer with despondent verbal messages, delivered visually in a beguilingly upbeat manner. Jenny Holzer has inscribed “What urge will save us now that sex won’t” onto a white marble footstall. McDermott & McGough have emblazoned the sadomasochistic song lyric, “Violate me / in violent times / The vilest way / that you know / Ruin me ravage me / Utterly savage me / On me no mercy / Bestow” in multicolored letterpress fonts on a turquoise ground.Alejandro Cesarco has printed “When I am happy I won’t have time to make these anymore” in pretty colors on a page.

Other exhibits render the macabre in saccharine colors and delectable surfaces. Folkert de Jong’s Polyurethane, silicone rubber, and Styrofoam sculpture “Dust” (2004) has a survivalist sitting astride oil barrels and supplies with guns,megaphones,and a kerosene lamp in nursery pink and blue. David Altmejd renders a cadaver in an advanced state of decay amid cracked mirrors and neon lights in “The Settler” (2005), a work of weird beauty.

There are pleasurable surprises in this studiedly strange show, among them Ann Lislegaard’s exquisite 11-minute video installation, “Bellona (After Samuel R. Delany)” (2005). This quotes a passage from the cult sci-fi writer about an imaginary city where subterranean motors rearrange the streets after visitors have passed through them. It then segues into gorgeous video animation of rooms melting into color-coded reconfigurations. Emerging from the subdued mystery of Ms. Lislegaard’s installation, it really is a brighter day.

“Nightmares” until July 8 (526 W. 26th Street, second floor, between Tenth and Eleventh Avenues, 212-627-3363). Prices: $4,000-$10,000. “Re: Location” until July 28 (132 Tenth Avenue at W. 19th Street, 212-367-7474). Prices: $3,500-$60,000. “Brighter Day” until July 14 (533 W. 26th Street, between Tenth and Eleventh Avenues, 212-714-9500). Prices: $1,000-$80,000.