He was an inmate at Sona that Michael Scofield was forced to break him out in order to save Sara and LJ.
He was a fisherman that one day took a job that consisted of taking a person to a place so he could took a water sample. He got a call of people wanting to know the exact place he took that guy. Whistler had a book he kept with details on his trips, so he was able to decipher the coordinates.
Later it was revealed that all of this was probably a lie, since the company didn't wanted any coordinates, actually what they wanted was to retrieve their lost agent. Whistler had a secret agenda and was trying to get his hands on Scylla, it is safely assumed that Gretchen did knew what he wanted, but was never revealed. The book with the supposed coordinates actually contained valuable information on finding Scylla, including the blueprints of the place it was kept.
It is unknown at which point of his life he met Sophia Lugo, his girlfriend throughout the series, to whom he kept secret that he was a Company Agent.
Before he could do anything the company wanted he was put under arrest for fighting and beating a guy at a bar, he was actually the son of the mayor at that city ad was sent immediately to Sona.
Hiding inside Sona.
As soon as he got into Sona, Lechero that was running that place put a price in his head, since the mayor had interest in finding him, so Whistler fearing for his life hid himself in the sewers of the prison and survived by eating rats he could catch.
Brad Bellick that was at the sewers cleaning some stuff for the rest of the inmates heard a noise and discovered Whistler's hideout. Whistler saw this as an opportunity and gave him a note that should be put into the pockets of the next two people that got into a fight, in that way letting the note out of the prison when the dead body was taken out, so his girlfriend Sophia Lugo could grab it.
It turned out that by destiny Michael Scofield was one of the guys that got a note, he of course was not the one to die and tricked Bellick into telling him where he got the note. Michael found out what Lechero said about Whistler and managed to find a way to Lechero let Whistler roam around free at the prison and take the ransom out of his head.
Sophia visiting Whistler.
While Michael was fixing a water supply problem at the prison to assure Whistler's freedom, Alexander Mahone was becoming desperate to be at Sona, and also found out where Whistler was hiding, he went to look for him and dragged him outside, when he turned him in to Lechero he said that Michael did a better job and he would honor his word of letting Whistler be at the prison. -
First escaping attempt.
The bird book.
The note he gave Bellick to give Sophia were the directions and the number of a bank account, she went to look what he wanted her to grab but only found a bird book. She was confronted by Lincoln Burrows that took the book as insurance. This book supposedly kept the records of all his travels and was the way he will find out exactly where he took the guy the company wanted to know.
Gretchen Morgan also confronted Lincoln and told him that he should return the book to her, after supposedly killing Sara she menaced to also hurt LJ so Lincoln had no other choice. Later Gretchen went and visit Whistler at Sona and returned the book to him.
Mahone, Michael and Whistler at Sona.
Michael, Whistler and Mahone started working on a plan to escape, it consisted to climb through the window out of Michael's cell in day light, just at an specific time when the tower guards won't be able to see them, Michael also found a way to trick the electricity at the fences to pass through them. When the day of the escape came only Michael and Whistler tried to get out, leaving Mahone behind but the escape plan failed and they were forced to return to their cells before the were catch up.
During all the time he waited there he began befriending Mahone, at first to find out things about Scofield, since both Whistler and Scofield were always doubtful about the other one.
Second Escaping Attempt.
Preventing the escape.
He received another visit from Gretchen, this time she told him a whole another strategy was on the way, this time the company themselves were breaking him out of Sona, he had to get into a high place and helicopters will be sent to catch him up. When the helicopters came they began shooting every guard in the way, Whistler was about to leave when Michael found him and grabbed him, when he was getting to the helicopter, finally both of them fell to the ground and Whistler was unable to leave.
After the helicopters incident Scofield was taken for interrogation, he surprisingly told everything to the officers, how he was put there to take Whistler out and that he was planning the escape since the first day he got there. They of course went and grabbed Whistler, he wouldn't tell anything, after some extreme interrogations methods he also spoke out, he even gave Gretchen's name. Gretchen later killed every guard that knew anything and both of them were returned to their cells.
Michael now had to come up with a new escaping plan, this time not only Whistler and Mahone were part of it but he was forced to include Lechero, T-Bag and Bellick. They were breaking out from under Lechero's room that only him had access to. After many events Michael made a plan and tricked Lechero, T-Bag and Bellick, they were used as bait so him, Whistler and Mahone could get out, and they did.
Once they were outside he tried to escape from Michael and Lincoln but was reached by them before he could get to Gretchen. Once they were all reunited the trade was made, Whistler in exchange of LJ. When him and Gretchen were about to leave, Sophia was curious why Gretchen haven't said anything about the coordinates the company wanted and Gretchen told her to wake up there were never coordinates, they just wanted their agent back, Sophia was hurt for all the lying and decided to stay with Lincoln and let Whistler go with Gretchen.
The brothers took their way and Whistler asked Mahone if he wanted to work with him, Mahone accepted the offer.
Looking for Scylla and Dying.
Whistler before dying.
Three weeks later he was in the middle of a process, selling one Scylla card to someone, which was worth 50 millions dollars. He did it but then killed the person, as he was about to copy all the data he was surprised by Michael Scofield who was following his tracks, Michael wanted revenge on Gretchen for killing Sara. After finding out Sara was still alive he decided to leave them and go look for Sara.
Wyatt retrieving the Scylla card.
The card was to be given to a businessman but Whistler gave him the copy, he was planning to take down the company through Scylla. Mahone contacted Scofield and told him about Whistler's real plans and they all met, just when Whistler was about to tell everything to Michael he was shot in the head by Wyatt, whom later grab the Scylla card from Whistler's jacket. -
Personality and Traits.
Since he only appeared on the third season of the series, his personality wasn't exactly fully developed, but still he managed to maintain an interesting enough character.
Despite the actor Chris Vance being British, his character on the show was Australian, he even talked with an Australian accent.
He often acted in a calm way, with suddens burst of rage towards Scofield when the plans were not going according. This probably was part of his charade as a simple fisherman that was caught without purpose in The Company affairs, so he had to keep his cool and pretend to just go with the flow.
The constant mystery surrounding the character was a main part of it, Scofield wasn't sure of what he really was until the very last moment. The character died before he could truly show how he would act without having to hide his motives.