n a dark night in New York City's Riverside Park, two rival groups, called the Greens and the Grays, are engaged in a grim ritual in which they will take the life of a 12-year-old girl named Melantha Green, with the goal of assuring a truce between them. As she is being strangled, someone swoops down and rescues Melantha, taking her away before the others can stop them.
Roger and Caroline Whittier, a young Manhattan couple, are walking home after seeing a play at Columbia University when they notice the lights dim on the deserted street, and are approached by what seems to be an injured mugger. But instead of robbing them, the young man, named Jonah, asks them to take care of a young girl who herself appears to have been attacked, and gives them a strange handgun. Roger and Caroline take the girl back to their apartment and call the police. But when the police arrive, the girl has mysteriously disappeared, only later to reappear. Later, Roger hears intruders on his balcony, believes he sees people crawling on the walls of his building and finds that the strange gun has also disappeared.
Roger and Caroline try to gain Melantha's confidence the next day, but she is reticent to talk. Roger learns where her family lives and visits their building, where he gets a wary reception from a woman named Sylvia Green, who demands the girl's return. Returning home, he is intercepted and taken to meet Torvald Gray, who also urges Melantha's return. Roger instructs Caroline to take Melantha to a friend's house, missing a visit by investigating NYPD detectives, including a wily 30-year veteran named Tom Fierenzo. While at the Whittier's apartment, Fierenzo hears a phone message from one of the Grays warning that failure to return the girl could result in "spilling the blood of thousands of New Yorkers."
At first separately, and then together, the Whittiers and Fierenzo doggedly try to determine what is going on. Over the next few days, they learn that the Greens and Grays are two rival groups of aliens living in New York City who came to this world more than 70 years ago, fleeing a war caused by a misunderstanding, only recently learning of each other's existence. The Greens can meld into trees and have specialized mental abilities, while the Grays can climb walls, disappear chameleon-like and have high-technology devices. Melantha's sacrifice was agreed upon by the leaders to keep her soon-to-develop mental powers from destabilizing their balance of power.
With the help of Otto Velovsky, a young Ellis Island clerk when the groups arrived and the only human who has since know about the Greens and Grays, Roger, Caroline and Tom must find a way to avert the war that is brewing between these small but powerful groups to save New York City from devastation.
A good sci-fi detective story
The Green and the Gray is primarily a detective story, and Zahn does an excellent job in plotting a compelling tale, as the protagonists solve the mystery of the Greens and the Grays and resolve their dispute. Although the novel starts slowly, the pacing steadily accelerates to a satisfying conclusion. There are only a few occasions where the Whittiers or Fierenzo comes to a conclusion on too little evidence and the authorial pulling of strings becomes distractingly visible, a common problem with many SF detective stories.
The characters are also adequately drawn, especially the Whittiers, although they feel more like a couple in their 40s than their 20s. Detective Sergeant Fierenzo is perhaps the most interesting character, and could have served a larger role in the book, as Zahn draws well on the standard archetype of the smart and resourceful veteran detective, willing to work outside the rules when necessary. The Greens and Grays are also interesting creations, although few of their large number are very well characterized as individual. Zahn is able to make it very conceivable that these strange aliens could have lived for 70 years among New York City's chaotic diversity.
The primary problem with the novel, however, is that it straddles uncomfortably between the unique and different requirements of urban fantasy and science fiction. While the best science fiction follows consistent rational logic based on known facts and science, the best fantasy follows a consistent emotional logic, often a kind of dream logic, where verisimilitude is created through things feeling right, even if they don't make rational sense. In The Green and the Gray, Zahn mixes the two disparate forms in ways that attenuate believability. While much of the novel is based on SF rationality, he also has some aspects of the Greens and the Grays—such as the Greens' ability to meld into trees and the Grays' ability to disappear, while each species can still pass for human—believable only as fantasy. It is as if there are two novels fighting for dominance here, perhaps either one of which could have been more satisfying than the mixture Zahn chose to write.
