The political balance is tenuous, and Shan must play the mediator between her anxious, disobedient crew and the powerful military force of these alien beings.

At the same time, she is troubled by her own past and the strange relationship that seems to be forming between her and Aras, as she struggles to lead a mission whose goal she doesn't yet consciously know.

Her destination is Cavanagh's Star; a planet hundreds of light years away, but with an atmosphere strikingly similar to that of Earth.

Knowing only that she was preceded on this journey by a colonist group named Constantine (who have never been heard from again), and that the time in speed-of-light travel will amount to 75 years on Earth but only months for her ship, Shan sets off in command of a mix-matched group of specialized civilians (called the "payload") anxious to use the planet for their own gain, and competing for control with Commander Lindsay Neville, the independent leader of a small force of marines.

Not only do they find Constantine alive and thriving as a religious colony within a carefully controlled biosphere designed to grow crops brought from Earth, but they also discover a unique and complex environment of alien plants and animals, including such species as the scavenger rock velvets, and the bog-dwelling predator shevens.

The Wess'har, who originate from Wess'ej, the planet's moon, are strong environmentalists who see each species as an intelligent race; they are vegan, and take pride in the fact that their architecture is subterranean and unobtrusive.

For centuries, they have protected Cavanagh's Star and the Bezeri from the Isenj - a third alien race who once attempted to colonize the planet.

When the pollution from Isenj cities which they had built on the planet got so bad that it was killing Bezeri by the millions, the Wess'har stepped in.

Now, not a single trace of the enormous Isenj civilization can be found on the planet - a stunning example to Shan's crew of what the Wess'har military is capable of.

According to the agreement between Shan and the Wess'har (made through Josh), the Thetis has been allowed to land and to make camp within the boundaries of Constantine.