Year of Hell

A huge ship appears in the sky above an alien colony and fires an energy beam, transforming the city into mountains and fields. As the wave encompasses the planet, the ship's crew comment on the colony's erasure before targeting the species' homeworld.

On board Voyager, Seven of Nine (Jeri Ryan) and Harry Kim (Garrett Wang) have developed a galactic map which should shave five years from their journey. Seven informs Captain Janeway (Kate Mulgrew) that the area of space they are in belongs to a species that the Borg know as the Zahl. Upon entering this space, a small vessel appears off of Voyager's port bow and begins an unprovoked attack. The ship is a Krenim destroyer, and the captain of the vessel declares that Voyager must leave Krenim space or be destroyed. As the ship's weapons prove useless against Voyager's hull, Janeway ignores the ship and proceeds to negotiate with the Zahl, who disdainfully threaten the weaker Krenim vessel. During their discussion, Tuvok (Tim Russ) observes that a temporal disruption involving the homeworld of the Zahl race has just occurred. As they try to understand what happened, a wave of temporal energy reaches their sector of space.

The wave wipes the Zahl race from existence while making the Krenim vessel bigger and more powerful, and reducing Voyager to a severely damaged state. Now aggressive and more arrogant, the Krenim captain tells Janeway that Voyager must submit to the Krenim Imperium and prepare to be boarded. Janeway takes advantage of Voyager's speed to escape. A scan of the region in the new Astrometrics bay reveals that Krenim warships dominate this region of space and it will be difficult for Voyager to sneak past them.

Voyager begins a running battle with many Krenim ships over a period of two months, suffering heavy damage and casualties. During one attack, Seven of Nine uses an unexploded Krenim chroniton torpedo to devise a method of shielding Voyager against the weapons; however, the weapon partially explodes, blinding and severely burning Tuvok. When utilized, the shielding also affects the temporal waves in the region, attracting the attention of the Krenim "time ship", the large vessel that is causing the disruptions. Krenim scientist Annorax (Kurtwood Smith) built the ship to cause "temporal incursions" to be used to erase events from history to strengthen the Krenim Imperium. However, a prior incursion caused a plague that killed millions of Krenim, including Annorax's wife, and he has been seeking a full restoration of his species for the past 200 years. Annorax decides to destroy Voyager due to the temporal distortions caused by its shields. The crew escape as Voyager is faster, but more damage to the ship ensues. Janeway orders all but the senior staff to abandon ship. She and the senior staff intend to rescue Commander Chakotay (Robert Beltran) and Lt. Paris (Robert Duncan McNeill), who were abducted by the time ship.

Captain Janeway makes an alliance with local races to attack the Krenim time ship. The senior staff move to the allied ships while Janeway remains behind on Voyager to pilot the heavily damaged ship herself. With the help of a dissatisfied crew member, Chakotay and Paris take the time ship's temporal core offline, rendering it vulnerable to attack, and beam to the nearest allied ship. Using conventional weaponry, the time ship disables the allied ships. Voyager is crippled when one of the ships collides with her. Theorizing that the original timeline may be restored if the Krenim ship is destroyed by its own weapon, Janeway orders the fleet to drop their temporal shields and rams Voyager into the time ship while it is powering up for another incursion. Voyager is destroyed, while the Krenim time ship's temporal core destabilizes and explodes. This erases the time ship from history, resetting the timeline. As his ship is erased, Annorax witnesses his wife's lock of hair vanish and appears to realize the significance of what is about to happen: reversing all of his changes will bring Annorax's wife back as well, fulfilling his ultimate goal.

In the original timeline, Voyager once again ventures into Krenim space. This time, the captain of the Krenim warship is moderate: he advises Voyager that "this area of space is under dispute" and suggests they avoid it. After giving the command to plot a course around the disputed space, Janeway remarks to Chakotay that she is thinking of replicating a bottle of wine for Voyager’s re-dedication ceremony, saying the vintage is a "good year". Elsewhere, Annorax works diligently in his study. His wife (Lise Simms) enters and asks him to enjoy the day with her. Annorax hesitates for a moment, and then decides he can "make the time" for her. They leave while his work remains on his desk, depicting the calculations for his initial alteration of the timeline.