Detection of an Omega particle puts all other priorities and Starfleet directives on hold. Janeway is duty-bound to destroy that particle above all else, but Seven objects.
Voyager's sensors detect a rare particle capable of damaging subspace and nullifying warp travel. Under a classified directive known only to Starfleet captains and above, Janeway leads Voyager on a mission to destroy all traces of that particle, but Seven of Nine hesitates to destroy it, sharing the Borg reverence of it as the embodiment of perfection.