At the end of the pervious volume, Cohesion, the crew discovered that Tuvok was missing from the ship. Scanning the surrounding space they discover he is on-board a shuttle heading directly for a space station orbiting a black hole. Shortly after arriving at the station he regains consciousness and realises that he has crashed the shuttle and is very seriously injured and possibly beyond the skills of Voyager's doctor.

Meanwhile, back on Voyager, there is a new member of the crew - Janeway's sister, Phoebe - but although you (the reader) know that she has never been on board, the rest of the usual crew seem oblivious to the fact - except for Harry Kim and Naomi Wilder. But why do these two see the truth that apparently evades everyone else?

Soon the crew find themselves facing a dreadful decision. The space station apparently contains technology that could greatly reduce the time taken to get home but the price could be the lives of one or more of their colleagues. Will they find a way to return home without sacrificing someone or will the captain be forced to make one of those decisions that only a true leader can make?

Fusion is the second book in the String Theory series and follows the adventures of the crew of Voyager during their attempts to make their way back to Earth. At the end of the previous book we were left with Tuvok having gone AWOL. At the start of this volume the crew have finally located Tuvok and are following him towards a space station that is apparently orbiting a black hole.

What follows is a more spiritual story, much of which is set in Tuvok's mind as he communicates with the spirits of the crew of the space station and is invited to leave his corporeal form and join them. At the same time the Captain is trying to discover the truth about an artefact given to her in the previous book.

As the story progresses it becomes clear that only Harry Kim, Naomi Wilder and the doctor realise that Phoebe Janeway isn't all she claims to be. The reason for this is quite neatly tied into an earlier episode - I won't go into any more detail, as it would spoil part of the plot. Just let it be said that this was a clever use of an earlier plot line.

This is another enjoyable Voyager book that leaves the story with a classic cliffhanger and I, for one, can't wait to see how this particular storyline pans out.

Synopsis
When Captain Janeway orders the investigation of a peculiar and dangerous anomaly tied to an alien civilization, it sets in motion a chain of events bridging Voyager's past with its future, forcing choices upon the crew with terrible repercussions, and discoveries beyond their wildest expectations. In this second novel of an exciting 3-part odyssey, Tuvok, Voyager's Vulcan security chief, answers a cosmic siren song that puts him on the verge of startling transformation, testing the crew's continued cohesion by challenging its assumptions about loyalty, duty, free will, and friendship.