In his bright introduction to this mediocre horror collection, Clive Barker refuses to ""spoil [the reader's] pleasure by hinting at the contents of these tales."" A wise decision; this fourth in a series, each volume of which offers original tales by three occult-fiction writers, is the sloppiest to date, hack work by writers who have done much better elsewhere. The biggest name here, the increasingly popular Dean Koontz (Phantoms, Strangers, Watchers, etc), leads off, but his three stories display little of the comparatively complex vision of his recent novels; two of the tales settle for pulpish action and the third for mawkish platitude. The pulp tales--""Miss Attila the Hun"" (another flogging of alien mind-invaders) and ""Hardshell"" (wherein a cop pursues an inhuman killer)--do provide a few light thrills; ""Twilight of the Dawn,"" however, despite its eerie overtones of Oscar Wilde's fairy tale ""The Selfish Giant,"" remains unconvincing in its exposition of a faithless man's turn toward the spirit. The next writer up is the less well-known Edward Bryant, who contributes six nasty nuggets yoked together both by an adolescent wallowing in such atrocities as rape, murder, and blood revenge, and by afternotes posturing darkness at the author's heart (""We [writers] are to suck the lifeblood from the lives around us in the manner of vampires. . .there are no experiences too dreadful to cannibalize""). Saving relative best for last, novelist Robert R. McCammon (Mystery Walk, Swan Song) closes with by far the niftiest tales here--""The Deep End,"" a fast, involving account of a man battling an underwater monster; and ""A Life in the Day of,"" an effective moral fantasy about the dangers of rushing through life. But even McCammon slides into slush with ""Best Friends,"" low-grade rip-'em-up fare detailing demons loose in a hospital. These night visions are dim indeed.