Mankind is spreading through the Solar System but, as yet, is still alone in the vastness of space. That is all about to change. A small team of intrepid scientists and engineers have made the long trip through the dark to Jupiter's moon, Europa, and set up camp on an icy plain under the looming watch of Jupiter above them. Initial samples show that the planet is host to primitive, unicellular life. A submersible makes its first dive under the moon's icy surface and finds signs that the life forms may not be quite so primitive after all. They uncover an indigenous species that shows signs of being capable of swarming together to achieve goals impossible for a single cell, a colonial organism that they nickname Opa. These Opas swarm in several different configurations in the cold dark ocean beneath. The teams A.I. is set the task of deciphering the science behind the Opa's dances, a swirling, and swooping that looks very similar to the movements of great flocks of birds back on Earth. Science is done, samples are taken back to the lab on the surface... and that's when the trouble begins. The Opas have been given a chance to roam in a new environment. A human environment. Mankind is not the only species hungry for exploration. The Opas escape into the expedition's living quarters. They are curious, and hungry. They are voracious for food... And they will kill every living organism in the space station!