In 1983 the Wichesters welcomed there second son into the world, Sam. On Sam's sixth month birthday his mother Mary checks in on him only to find a mysterious man standing over his crib. Sam's father John hears Mary scream and then runs to the nursery to find Mary pinned to the ceiling then burning into flames. After 22 years while Sam was attending College at Stanford University on Halloween his brother Dean breaks into his apartment with whom he shares with his long time girlfriend Jessica to tell Sam that there dad is missing and he needs his help to find him. Sam refuses to go with Dean because he swore he was done hunting but after hearing John's last message to Dean Sam agrees to go with him only for a few days. When Sam gets back his girlfriend Jessica isn't home so he retreats to his bedroom only to find Jessica pinned to the ceiling and buring into flames as his mother did so many years ago.
Later in Season One Sam tells Dean that he dreamt about Jessica's death before it happend he just didn't think it was true. His premonitions have lead him to saving a single mom with two children, another family from the same tragedy he went through, other people with powers simular to his not using them for the right reasons such as murder, & to a town full of people with a demon virus aka "Croatoan".
At the end of Season Two the demon Azazel who gave Sam his powers shows him what really happend in his nursery on his sixth month birthday he shows Sam a flashback and realizes his mom knew the demon also seeing him putting demon blood in his mouth which later gave Sam his powers. After losing his life in "All Hell's Breaking Loose" his brother Dean goes and makes a deal with a crossroads demon to bring Sam back to life for only One year to live, Dean accepts the deal.
Throughout Season Three Sam trys everything to get Dean out of his contract but is unsuccessful. Sam having to hunt alone he turns to Ruby who suggests drinking demon blood to make him strong enough to pull demons out of there bodies & help saving people without killing them.
In Season Four after Dean is resurrected from hell by Castiel Dean realizes how bad Sam has really gone when Castiel tells Dean to either stop his brother or they will. Sam stops using his powers for awhile but always finds himself resorting back to it. At the end of Season Four Sam uses his powers to kill Lilith which set Lucifer free and began the Apocalypse.
In Season Five Sam doesn't use his powers much but suffers like any recovering addict still wanting demon blood. Later in the Season Sam decides that he is going to let Lucifer have him as his vessel and has to drink several gallons of demon blood to prepare for the battle that awaits him. In "Swan Song" Lucifer/Sam goes up agaisnt Michael/Adam for what they each want there world to be. Lucifer/Sam grabs Michael/Adam into the pit of hell to end the Apocalypse once and for all.
Unexpectly Dean finds out in the beginning of Season Six that Sam has been alive and out of the pit for the whole year that he was to believed to be dead. It was later revealed that the demon Crowley was responsible for getting Sam out of hell, however he left something of Sam's behind his soul which makes it impossible to have feelings, emotions, or sleep. Determined to get his brothers soul back Dean visits "Death" to see if there was anyway for him to get Sam's soul back without all the torture Lucifer & Michael put on it. Then "Death" says yes he could put up a wall how long the wall stays up is up to Sam.
What we can expect when Sam gets his soul back is unknown.
I'm hoping to see the old Sammy back the one we all miss and have grown to love throughout the years.