In 2381, the USS Voyager was a part of the fleet that gathered in the Azure Nebula to combat the Borg Collective during their invasion. Over 7,000 Borg cubes emerged from a subspace tunnel and simply rammed through the fleet. As a result, many on Voyager were killed, including Doctor Jarem Kaz.
As part of Project Full Circle, Voyager was equipped with a quantum slipstream drive and returned to the Delta Quadrant. Doctor Sharak was assigned as Jarem Kaz's replacement. (VOY novel: Full Circle)
Toward the later part of 2381, Sharak began to become more comfortable serving aboard Voyager. He also found himself speaking Federation Standard easier than before, but still used the typical language of Tamarians to convey emotions. Sharak eventually made a working translation to the entities known as the proctors, who began to communicate through images taken from Voyager and USS Demeter. Upon realizing the nature of the pictures indicated emotion, he was able to put the pieces together from there and communicate easily. He later asked the proctors for the proverbial "key" into the "stream", which led to the Confederacy of the Worlds of the First Quadrant. (VOY novel: Protectors)