Binding Ghosts is a spell that allows a person to bind a ghost to their will to perform whatever task they demand, including murder.
Wanting revenge on other psychics both real and fake as he is not famous like they are, Jimmy Tomorrow steals the bones of Margaret Fox and casts this spell to bind her to his will to use her to kill his competition. Under Jimmy's command, Margaret kills Imelda Graven, Grandma Goldy, Nikolai Lishin and Camille Thibodeaux while her sister, Kate Fox, tries to warn people with visions of their deaths.
After hearing about the murders of Imelda and Goldy, Sam and Dean Winchester come to Lily Dale to investigate, at first wrongly believing that Kate is the killer. After discovering that it is Margaret from her murder of Camille, Sam and Dean find her bones gone when they go to salt and burn them and realize that someone is using this spell which they refer to as "serious binding magic." Eventually tracking Jimmy down while Margaret goes after Melanie Golden, Sam breaks the spell by knocking over the altar that is part of it, but as Margaret is actually happy to kill for Jimmy even without the "leash" of the spell, Sam is forced to salt and burn her bones to stop her.
In order to perform the spell, the caster must have an ashwood altar as well as the bones of the ghost they wish to bind. Along with the other ingredients, the skull of the ghost is placed in the center of the altar and the altar must remain undamaged for the spell to work though if the skull is removed it doesn't seem to affect it.
Knocking over the altar and its ingredients breaks the spell which is described as putting a "leash" on the ghost so it does whatever the caster wants while the spell is in effect. While the spell summons and binds the ghost, if it is broken, the ghost won't disappear if they choose to continue the actions they are forced into doing by the caster on their own.