During the effort to stop the Apocalypse, the King of the Crossroads and rogue demon Crowley approached hunter Bobby Singer about making a deal to find the Horseman Death. According to Crowley, he needed Bobby's soul to power a spell to find Death and promised to give it back to Bobby afterwards. Bobby ultimately agreed to the deal and Crowley was able to find Death, but refused to return the soul until after the Apocalypse was over to ensure Sam and Dean didn't kill him. Crowley promised to break the deal afterwards and even used the deal to restore Bobby's legs which had been rendered useless by an attack by Meg and her demons, something Bobby hadn't even considered asking for.
Following the end of the Apocalypse, Bobby summons Crowley in order to get him to uphold his end the deal. However, Crowley instead smugly shows Bobby the contract on his body which states that Crowley only has to make "best efforts" to give him back his soul and he doesn't intend to do it. Crowley tells Bobby he'll give him ten years instead before he collects his soul, but Bobby tells him that he'll hold Crowley prisoner until he changes his mind as Crowley has just walked into a devil's trap made of ultraviolet paint. However, Crowley anticipated this trick and brought his hellhound. Crowley threatens to have the hellhound take Bobby to Hell now instead of in ten years if he doesn't break the trap and Bobby reluctantly does so. Before Crowley leaves, Bobby promises to keep trying which just amuses Crowley.
A year later, Bobby still continues his efforts and manages to capture a Crossroad Demon and get her original human bones. Bobby demands Crowley's real name from when he was human from the demon who simply taunts him about killing his wife. Bobby then reveals he has the demon's original human bones though she claims that burning their original bones hurting demons to be a myth. Bobby begins burning the bones with a flamethrower which also burns the demon and causes her great pain, however, she refuses to give him Crowley's real name as Crowley is now the King of Hell which Bobby didn't know before. The two are interrupted briefly by Bobby's neighbor Marcy who the Crossroad Demon tries to call to for help, but Bobby just passes it off as a horror movie on TV and Marcy leaves, none the wiser. Bobby returns to the Crossroad Demon who taunts him about Marcy, but Bobby just starts using the flamethrower to burn her bones again and cause her great pain, demanding Crowley's true name all the while. The demon finally gives in and tells him Crowley's real name is Fergus MacLeod and the demons call him Lucky the Leprechaun behind his back. Bobby informs the demon that Fergus is a Scottish name not an Irish one and that she's an idiot. The demon asks Bobby to exorcise her now that he's got what he wanted, but Bobby instead starts pouring lighter fluid over her bones to her horror as she thought he'd let her go afterwards. Bobby simply tells her "I gave it my best effort" and torches the Crossroad Demon's bones, killing her and causing her and her vessel to burn to ash.
Now having Crowley's name, Bobby begins looking for his resting place in Scotland. When Rufus Turner shows up for help disposing of the body of an Okami, Bobby tells him of his search and that Crowley dropped a clue at to where he's really from when they met to discuss breaking the deal: he likes Craig Scotch which is only made and sold in a tiny area on the northern tip of Caithness county. Bobby guesses that's where Crowley lived and died when he was human before he became a demon and Rufus, who has contacts in that area, offers to help him with his search for information. After Bobby deals with the Okami who Rufus didn't kill afterall, Rufus informs him that he found something on Crowley who was born Fergus Roderick MacLeod in Canisbay, Scotland in 1661. Rufus has discovered that Crowley had a son, Gavin MacLeod who captained a trading ship that went down in 1723 off the coast of Massachusetts. The wreck was found 30 years before and though Gavin's bones were never recovered, his signet ring was and is now in a maritime museum in Andover, Massachusetts. Bobby asks Rufus for his help in getting the ring and Rufus agrees, thinking Bobby intends to summon Gavin's ghost and exchange him for his soul to Crowley. As Dean calls to ask about how weird his brother is acting Bobby gets a call from Rufus who was spotted breaking into the museum and is now being chased by the police. Before Rufus is arrested, he swallows the ring against Bobby's advice. When Bobby switches back to Dean, he gets angry when Dean accuses him of being selfish and yells at him and Sam for their behavior. Humbled by his outburst, the Winchesters agree to do whatever they can to help Bobby break his deal. Bobby then sends them to Scotland to be ready once he locates Crowley's grave. Needing to get to Rufus and the ring and knowing that the FBI are after him for murder, thinking he murdered the Okami, Bobby approaches Sheriff Jody Mills for help by getting her to extradite Rufus to Sioux Falls for murder. Jody is shocked and refuses as it could cost her her job and cause her a lot of trouble. However, later that day, she changes her mind and brings Rufus to Bobby, telling them that she's going to give them an hour and then call the FBI and tell them that Rufus escaped from her custody. Rufus is able to give Bobby the ring which he has retrieved from his stomach by the time he reached Bobby's house.
Now having the ring, Bobby summons the ghost of Gavin MacLeod to question him about where he can find his father's bones. Once Gavin hears what Bobby wants, he happily gives him the information as he hates Crowley. Bobby then passes the information onto Sam and Dean who locate and dig up Crowley's grave. Once they have his bones, Bobby summons Crowley once more into a devil's trap. Crowley is simply amused as he thinks he holds all the leverage and complains about the problems of his new position of being in charge of Hell. Crowley eventually mocks what he thinks will be Bobby's speech, but Bobby reveals the ghost of Gavin who is watching the whole thing. Crowley initially pretends to be happy to see Gavin, then laughs because he thinks that Bobby intends to trade Gavin for his soul. Instead, Crowley tells Bobby to torture Gavin all he wants and he'll enjoy watching it. Bobby then reveals that he wasn't using Gavin as a bargaining chip but to get information and as Gavin hates Crowley even more than Crowley hates him, he was more than happy to tell him what he wanted to know. Gavin informs a horrified Crowley that he told Bobby everything before disappearing. Bobby then taunts Crowley about how he sold his soul "for an extra three inches below the belt" and after telling him he now knows where Crowley is buried, tosses him the phone with Dean on the other end. Dean informs Crowley that he and Sam have dug up his grave and now have his bones. Crowley quickly tells Bobby that burning a demon's human remains to kill them is a myth, but Bobby informs him he used that method to kill his Crossroad Demon whose whereabouts Crowley had been wondering about. Bobby tells Crowley that the new deal is he releases Bobby's soul from his contract or Dean burns his bones and kills him. Crowley hesitates, but ultimately gives in and breaks Bobby's deal. Bobby reminds him to "leave in the part about my legs" and Crowley does, allowing Bobby to retain the use of his legs the deal had restored.
With their business concluded, Crowley asks Bobby to let him out of the devil's trap. Bobby does and Crowley travels to Scotland with a bag to collect his bones. While Dean considers still burning them and killing Crowley, Sam tells him a deal's a deal and allows Crowley to collect his bones and leave.
Though Castiel apparently finds the bones later and burns them to kill Crowley, this is actually a trick as the two are working together to hunt for Purgatory. Its later revealed that Crowley's bones are kept in a MacLeod crypt in Guam after he takes them. Its where he later hides the First Blade also.
Despite Crowley breaking Bobby's deal, when Bobby's ghost is put to rest he gets a rogue Reaper named Ajay to take Bobby's soul to Hell instead of Heaven where it belongs. After learning of the truth during the Trials, Sam travels into Hell and rescues Bobby, eventually getting him into Heaven with the help of Benny and Naomi.