Picture this: A woman runs away from a husband who has several wives, gets hit by a car and develops amnesia, takes a room in the apartment of the man who caused her to lose her memory, and travels 3,000 miles across the country with him and his trusty cat. Add to this: a chase led by the extortionist husband, a death wish by the girlfriend of the man with whom she travels, and a traveling curse in the form of a little blue suitcase filled with smuggled jewels. To make matters more complicated, the lost woman has a long list of created aliases and a penchant for storytelling.

These are the ingredients of Kate Wilhelm's 21st novel, "Oh, Susannah!," and the exclamation point says it all. The author is well aware of how to create a fast-moving, entertaining novel that is exciting and, above all, vivid. The form is "story within a story," as characters from different lives, different states and different age groups manage to get entangled with one another, and with a central character whose loss of memory makes entanglement a way of life.

Kate Wilhelm makes her fantastic tales seem almost plausible by creating odd but believable characters. She gets at those very details that make people tick. For example, the main character, Susannah, a "slender young woman" with "sun-bleached hair," has a knack for suiting stories to her audience: "She had an uncanny vision that let her pierce the superfluities of the listener, see into the core of the person she was telling a story to." Her new companion, Brad, a 12th-century literature scholar working on his doctorate, is also a very poor driver--one of those people who always "prefer to drive in the left lane where they feel they have more space," and who is "confounded by one-way traffic patterns." Donna, Brad's girlfriend, is described as "sleek-looking with shiny black hair and beautifully soft, cream-colored skin" and as having a mind "like a twisting maze with cunning traps, unexpected dead ends," but she is also "a fastidious person, had never played in mud, or with Play Doh, or finger paints. She refused all finger food, anything that could possibly run onto her hand, like ice cream, or watermelon."

Even the cat is not merely Siamese, with "short sleek fur": "It was a conglomerate cat, a poorly conceived corporation of cat ideas . . . It trusted no one, liked no one, was arrogant and demanding, had no redeeming virtue, and it was hypocritical."

Knit into the fabric of such elegantly described characters are certain small gems of truth that can only be conceived through the mind of the altered, at-a-loss-for-memory Susannah. "She did not know what was wrong with being herself, but she suspected that something was very wrong with it, she simply did not remember what it was." Susannah casually remarks to Brad, "I think everyone has amnesia; only most people won't admit it." She tells a religious youth, searching to help everyone, that "I think if you love everybody you can't love anybody very much."

Though the amnesic Susannah walks about asking "Do you know me?" of just about every stranger she comes across, she has not lost her sense of reality, but created a new, more interesting one. Her strange aliases -- inventions of lives never lived -- give this novel its flavor and excitement. She tells a little girl, "My name is Thalia . . . I am a fairy princess," or she shocks a women's forum by calmly explaining, "My name is Oshana, and I'm from a planet called Arretxul." Or she is Ingrid Morgan, daughter of a well-known archeologist and explorer of lost Indian cities in South America, or she is Marash, a Rumanian gypsy who has "the gift of vision."

Brad describes Susannah's behavior on a beach covered by an incredible fog by saying that "her fascination was contagious." Susannah's storytelling ways become equally contagious for the reader of this novel, who may just be moved to rush up to the next available stranger and ramble on about some fantastic previous life.