Once the Sole Survivor has gotten Valentine to like them enough, he will confide in them about his original life from before the Great War, and how the person that he has assumed the identity of, was also a great detective. He will go on to tell a story of Nick's greatest challenge, seen in the form of an untouchable crime boss by the name of Eddie Winter, who, even after confessing his killings and ratting out the people he worked with, was still unable to be held by the police.
Eddie Winters eluded justice, even up to the Great War, and has remained Nick Valentine's greatest shame, haunting his memories, even through the synth that has assumed his identity. Valentine will state that he believes that finishing the case will give him some closure on the life of the real Nick Valentine, believing that in order to create his own identity, he must do this first.
Nick Valentine will then have the Sole Survivor travel to various jails and prison stations, in order to collect holotapes recording the many confessions and gloating of Eddie Winters, all of which are revealed by Valentine to hold a secret number, which can be used once completed, to access a secret bunker where Winter hid to survive the nuclear war.
After collecting the holotapes and traveling to the secret bunker hidden away within Andrew station, Winter is found still alive, having used an experimental procedure to turn himself into one of the world's first ghouls. Without hesitating, or attempting discussion, Valentine will gun down the crime boss, finally ending his reign of terror.
Valentine will have one matter to attend to, in which he will visit the site where the real Nick Valentine's lover was gunned down by Eddie.
Find Eddie Winter's holotapes (10/10)
Nick asked for my help in recovering ten holotapes belonging to Eddie Winter. He thinks the Commonwealth's police evidence terminals should be able to point me towards the tapes.
Talk to Nick
I've found all of Eddie Winter's holotapes. I should turn them over to Nick.
Travel to Eddie's Hideout
Nick deciphered the code to Eddie Winter's bunker from the holotapes. Now it's time to head to Andrew Station and put an end to Eddie.
Access Eddie Winter's Bunker
Confront Eddie Winter
Nick and I killed Eddie Winter. Now Nick says he has one more thing to take care of. Suppose I should follow his lead.
Upon Eddie Winter's corpse, his personal firearm can be obtained, called Eddie's Peace.
Within Winter's hideout, a holotape can be found, revealing more about Eddie's life just before the Great War.