Twenty-seven years prior to the opening of the main story, four interstellar explorers in search of extraterrestrial life unexpectedly return home early from a mission. Two of the four disappear, and a third is killed in an inexplicable explosion that devastates a mountain on their home world. The fourth team member, the starship captain, never flies again and eventually dies in a planetary rescue mission far from his home. Although the authorities suspect foul play in the explosion, they have neither proof nor motive, and never solve the case.

What happened? And why?

This mystery forms the centrepiece of Infinity Beach. The main character, Doctor Kim Brandywine, is the younger sister of one of the missing explorers. A relative of the other vanished explorer convinces Kim to conduct her own investigation into what happened twenty-seven years ago.

Much of the action takes place on Greenway, a planet terraformed by humans to provide an idyllic life. Her people have achieved universal prosperity. Machines and AIs care for their needs, nearly everyone has a healthy youth ensured for most of their extended lives, and almost no crime exists. However, rumours of strange ghostly phenomena run wild in the region of the explosion. No one has brought forth any proof, though, and the stories are dismissed -- at least officially.

Kim is drawn into a puzzle that becomes ever more complex, involving incidents that happened far from Greenway, in interstellar space. McDevitt develops the mystery beautifully, introducing one clue here, another there, tantalizing the reader with bits and pieces of the puzzle. He draws in the players one by one, giving them intriguing personalities without resorting to clichés. By weaving this refreshing mix of characters in and among the clues, he makes the puzzle even more riveting.

Infinity Beach showcases world-building at its best. McDevitt constructs a believable society, with some of the better extrapolations into the far future I've read. Whether that era will actually turn out that way, who can say, but the story makes it convincing given the parameters in its set-up. Perhaps the most startling is this: despite the sophistication in AI, no construct has achieved sentience. The people on Greenway choose to perfect their human state rather than augment themselves by computer or android advances. Given these constraints, the society works.

The world, Greenway, it well described in all its quirks. McDevitt layers in the science with a light touch, using an expertise that will satisfy most hard SF readers while remaining unobtrusive to those with little interest in such aspects. Parts of the book take place in space, near a star in the belt of Orion. McDevitt creates the milieu with verisimilitude, successfully evoking a sense of incomparable beauty out among the stars.

The prose in this book pleases. Its clean, polished style flows well. A quotation precedes each chapter, many by fictitious luminaries of the future. It adds richness to the universe McDevitt creates, including touches of humour as well as an insightful look at human nature.

McDevitt has a knack for characterization. Kim is particularly strong; she comes across as self-confident, skilled, and likable, yet at the same time she is no paragon. She stumbles, then pulls herself up and continues on. McDevitt writes with understanding and compassion for his characters, making their tragedies and triumphs all the more poignant.

The most compelling subplot involves Kim's relationship with Solly, or Solomon Hobbs, a starship captain who starts out as her best friend. Solly thoroughly charms and, for the most part, plays an excellent role in the story. However, this also touches on the book's only weakness, if such a strong work can be said to have a weak point. I don't want to give away too much; suffice it to say, I felt the conclusion of this subplot was the wrong one for this book. The reason I had such a strong reaction, of course, is because McDevitt writes human interactions with such an appealing touch.

Infinity Beach is an engrossing science fiction mystery; one of the best I've read in a long time. In addition to telling a great story, it offers the reader thoughtful questions about what it means for humanity to mature rather than stagnate as a species. McDevitt has served up another exciting, literate yarn.