The guest who throws a family into crisis

Ben Franklin once quipped that visitors, like fish, stink after three days. He'd obviously never met Amber, the barefoot 30-something at the center of Ali Smith's novel The Accidental.

Amber turns up one day at the home where the Smarts are enduring their vacation, announcing, "Sorry I'm late. I'm Amber. Car broke down."

Michael, an English professor, assumes she's come to interview his wife, Eve, a bestselling author of "autobiotruefictinterviews." Eve assumes that Amber is the latest in Michael's long string of student-conquests. Astrid, 12, who's so bored that she's been filming dawns, is instantly fascinated. And Magnus, 17, who's consumed with guilt for his part in a nasty prank that caused a classmate to kill herself, thinks Amber is an angel (albeit one with dirty feet). But whether she's an angel of destruction or of mercy is an open question, depending on which character you ask.

In the confusion, Amber gets invited to dinner, and all the Smarts fall in love with her. She ignores Michael; taunts Eve; takes Astrid on field trips, then throws her video camera off a bridge; and saves Magnus from suicide, then seduces him.

"We'll be away about an hour, long enough for me to ravish him sexually then bring him back safely, is that okay?" she announces brightly to his parents, who laugh at this uproarious joke.

Not since Sheridan Whiteside inflicted himself on the Stanleys in "The Man Who Came to Dinner" has a houseguest caused such upheaval in a staid middle-class family. (Actually, the plot is apparently taken from a 1968 movie, Pasolini's "Theorem," starring Terence Stamp. Amber also is a close cousin of Will Smith's ingratiating liar in "Six Degrees of Separation," although she never bothers with charm.)

Scottish writer Ali Smith's sixth book won a prestigious Whitbread Award last week and was a finalist for the Man Booker Prize. (Like another Booker finalist, Zadie Smith's lovely "On Beauty," it's ultimately way more fun to read than the winner, "The Sea.")

"The Accidental" has some marvelous characterizations - Astrid is the book's crowning glory - and the writing brims with wit, humor, and energy. Smith gives each character their own style: Eve is interviewed Q&A-style, like her books; Astrid is stream-of-consciousness; while Michael holds forth as if he's lecturing to a hall of rapt freshmen (with mental asides to congratulate himself on his own cleverness).

Then he breaks into sonnets - and the poetry is as accomplished as Smith's impersonation of a clever, unhappy, foul-mouthed preteen. (Truly foul-mouthed - there's a prodigious amount of profanity and sex in the novel.)

One of the few facts we learn about Amber is that she was conceived in the Alhambra movie palace (Alhambra is really her name), and, in the book's weaker sections, she periodically holds forth on movies and their role in modern culture.

Magnus explains it all to Astrid much more simply, and without the endless lists of movies. "In a film there is always a reason.... Magnus held up a pen, then dropped it. He said if you drop a pen out of your hand in real life, that's all it is, a pen you dropped out of your hand there on the ground.

But if someone in a film drops a pen and the camera shows you the pen, then that pen that gets dropped is more important than if it's just a dropped pen in real life. Astrid knows this is true, but she is not completely sure how."

When Eve finally kicks Amber out of their house, some of the spark seeps out of the novel. The Smarts return to London to a plot twist that echoes British writer Alan Bennett's wise, witty "The Clothes They Stood Up In," and try to put themselves back together again.

Like Humpty Dumpty, they meet with little success, although the damage had been done before Amber ever walked through the door.

"Everybody at this table is in broken pieces which won't go together," Magnus thinks at dinner one night, "pieces which are nothing to do with each other, like they all come from different jigsaws, all muddled together into the one box by some assistant who couldn't care less in a charity shop or wherever the place is that old jigsaws go to die."

Amber is first shown as a bright blur in Astrid's video camera, and the question of what she is (ghost? fate? the collective unconscious of the Smarts?) and why she picked the Smarts is never answered.

If you're a mystery fan, like me, this is more than a smidge frustrating: If you're going to upend someone's life, there should be a reason. Michael, in particular, spends a fair bit of time on her identity: "Amber was an exotic fixative. Amber preserved things that weren't meant to last. Amber gave dead gone things a chance to live forever. Amber gave random things a past.... (Amber, in the hall, walked past Michael as if he were invisible, a piece of nothing, unbegun.)"

Another line offers a reasonable explanation for Amber's role. "Gypsies used amber as a crystal ball." For the Smarts, Amber operates as a prism through which they can finally see themselves.

• Yvonne Zipp is a freelance writer in Kalamazoo, Mich.