By Nick McDonell

Grove. 267 pp. $22

In 2002, at the astonishing age of 17, Nick McDonell wrote a fine novel about Manhattan called Twelve, which became an international bestseller and was highly praised for its mastery of teen-talk (comparisons with Salinger's The Catcher in the Rye were made). I'm prepared to bet that once the euphoria faded, McDonell became the victim of a form of panic that follows every such triumph: Can I do it again, or was it just a fluke? Shrewdly, he realized that his gift was all about the imaginative recreation of contemporary urban experience, but he didn't want to repeat himself; in other words, he needed another New York.

Sadly, for his second novel, The Third Brother, he has flown to Bangkok, a city he does not know or understand, and made it the centerpiece of his narrative for the first 158 pages. So we find ourselves in an incomprehensible landscape without a backup plan as various moronic, dope-driven backpackers come and go without explanation; a woman blows darts from her vagina; marijuana and yaa baa (methamphetamine) are everywhere; a corrupt cop inexplicably starts waving his gun around; backpackers and traffickers get into deals that go wrong; we are perpetually looking for a character called Dorr whose name appears with monotonous regularity, just so that we can exhale when he finally arrives.

The excuse for all this is that the central character, Mike, a journalist of little talent, has been sent to Bangkok to chase a dubious drug-trafficking story. He gets involved with a Thai woman named Tweety only to inadvertently cause her death. (It's terribly difficult to feel sad about the death of a two-dimensional character named Tweety.) This could all be fascinating, but not when it includes so many cliches from Bangkok noir.

Mid-book, however, everything changes; we are no longer watching a blushing young man walk into elephant traps in the exotic East. We are back in McDonell's hometown, where he needs no guide book and the cliches fall away. His treatment of the 9/11 catastrophe is masterly. He has telling detail at his fingertips, and the city constitutes a kind of internal map of his soul.

Alas, the metamorphosis is not enough to save the novel. The plot is no more than a desperate attempt to weld together two very different books. The second one shows promise, but it is only a hundred-odd pages long. If McDonell is planning his third novel, as I am sure he is, then he should adapt and adopt an ancient mantra: Stay West, young man. *

John Burdett is the author of "Bangkok 8" and "Bangkok Tattoo."