Caption: Locutus revealed
Caption: Enter Locutus
Caption: Locutus oversees the battle at Wolf 359
Caption: The Borg Queen with Locutus
Caption: Locutus on Saratoga's viewscreen
Caption: Locutus at Wolf 359
Caption: "Almost human..."
And that voice was dubbed Locutus of Borg.
Despite Picard's insistence that he would resist the Borg with his last ounce of strength, that resistance proved futile and he was assimilated into the Borg Collective. He became one with the hive mind; he had the Borg's cybernetic devices implanted throughout his body. Locutus' distinctive Borg feature was a single, red-laser ocular implant.
The crew of the Enterprise-D eventually managed to sever Locutus from the Borg Collective, save Picard, and ultimately defeat the Borg. However, the memory of Locutus would forever haunt the captain. The events at Wolf 359 crept up several times for Picard, most notably three years after the incident, when Picard met Commander Benjamin Sisko at Deep Space Nine. Sisko served aboard the Saratoga at Wolf 359 and lost his wife during the attack, a loss he blamed Picard/Locutus for.
Locutus plagued Picard yet again on Stardate 50893.5, when the moment Picard had been dreading for nearly six years had finally arrived: The Borg had begun a second invasion of the Federation. During this particular encounter with the Borg, Picard admitted that he could still "feel" the Collective, he could still hear their thoughts. Picard used his knowledge of the Borg to fight them, launching a vendetta six years in the making against the Borg Queen and her drones' plan to prevent Earth's first contact with the Vulcans and assimilate the Enterprise-E in the process.
During his confrontation with the the Borg Queen, Picard learned that she wanted Locutus to be more than a drone; she wanted Locutus to be her counterpart. Picard managed to defeat the Borg Queen and save humanity once again.