Dark matters. Book 1 Cloak and dagger - Christie Golden

Marooned in the Delta Quadrant light years away from home, the crew of the Starship Voyager have more than once stumbled upon what they thought was a shortcut back - only to have their hopes crushed. In one of the most memorable of these episodes, 'Eye of the Needle', Voyager discovered a wormhole that would take them to Romulan space - but twenty years in the past. Now in Christie Golden's powerful trilogy the Romulan scientist who created that wormhole, Telek R'Mor, is back.
An unknown species has adapted his theories on artificial wormholes, allowing the Romulan Empire of twenty years ago to create passage to the Delta Quadrant - and the USS Voyager - of today. The Empire wishes to capture Voyager, existing as she does in their future, in order to gain a twenty-year head start on Federation technology. The Shephards want Voyager for reasons of their own. But the technology they have developed involves the manipulation of dark matter, a dangerous undertaking with disastrous consequences for the Empire, for Voyager, and ultimately for the universe itself.
Before long Voyager and her crew begin to succumb to the effects of the dark matter. At the same time, Romulan saboteurs are discovered on board, Voyager is contacted by another mysterious species (this one claiming to come in friendship), a flock of Romulan Warbirds journeys into the present to seize control of the ship, and Chakotay and Paris disappear into an unknown alien realm...