Frightful Fiends: Two Novellas of Desolate Horror

The Omnibus edition of Death Shadows: The Flesh Eaters of Skid Row and Mutations of the Forbidden Zone. The two stories together in one volume.

Death Shadows:

On a sunny morning three homeless residents of an abandoned industrial park discover the corpse of a man lying on the pavement with a notebook of strange physics formulas. To the horror of the surviving witness, touching the remains causes two of them to instantly disintegrate into skeletons, their flesh chewed off the bone in seconds. Soon, a pair of drug dealers, two prostitutes and their pimp, three college students, a real estate agent and his assistant, and other vagrants of the inner city slum converge on the desolate territory and make the terrible discovery that they cannot leave. Any attempt to cross the shadows that ring the outermost boundary of the city block leads to instant death, for invisible monsters lurk in the absence of light along the decrepit buildings and fences, devouring those who try to flee.
To add to their dread, they only have until the setting of the sun to find a way to escape, before the entire territory of their phantom prison is swept over with the fatal darkness.

Mutations of the Forbidden Zone:

An archeology professor and his students embark upon a digging expedition in Nevada. But when his favorite pupil learns that he has been planting artifacts to boost his academic fortunes and vows to report him, he diverts their schedule to explore an old mining shaft in the foothills, hoping to use the distraction to persuade her to reconsider.
Emerging from the opposite end of a tunnel, they find a derelict airbase, seemingly abandoned since World War 2. The group branches out to investigate the site and are attacked by savage creatures up to fifty feet in height, forcing the survivors to run for shelter within the hillside caverns where a mysterious stranger awaits them. The star student finds herself caught in a desperate struggle between her former mentor’s determination to protect his interests and the colossal monsters of nuclear nightmare.