A ship that pushes ice -- puts massdrivers on big clumps of ice out in the Kuiper Belt and sends them back to their company, DeepShaft, on Earth -- is called to release the current ice bit and head toward Janus because it's started moving. As they head there, it becomes clear that Janus is a machine -- a spaceship -- and the head engineer, Svetlana, realizes that they don't have enought fuel to get there and back to Earth. The head of the ship, Bella, checks with the company (remember the name?) and they say, oh, plenty of fuel. This is where Bella and Svetlana stop being friends and start being enemies, which plays strongly on the story.
It's clear by the time that they get to Janus that they don't have the fuel and wait, Janus is pulling them with it, and it's headed toward Spica. They get there and a black cube with the Da Vinci figure is waiting and they find out the tube in Spica was an accelerator and they're much much further away from Earth. They're essentially in an alien zoo where the first set of aliens seem helpful, but others don't. Svetlana and Bella continue to battle until the end.
I liked this, but you do have to accept that we're not the smart, technologically superior species, and that humans can be sufficiently angry to jail someone for 13 years and to kill other people.