Supernatural: Red Sky at Morning
A jogger girl sees a pirate ghost ship on the horizon. It disappears before she can get a good look. Someone follows her home and kills her. Every 37 there is a ghost ship sighting and then a rash of dry land drownings. Seeing a ghost ship is a death omen.
The boys car is stolen in the middle of an investigation. Supernatural artifact thief Bella Talbot returns. She had it towed for fun. Later in the story Bela IDed the ship. It's actually a merchant sailing ship from 1859 (no pirates :( ). A 37 year old sailor was accused of treason and hanged. They also cut off his right hand to make a hand of glory. Bela wants to find and destroy this hand because that will stop the killings. She wants to do so because she has been hired by the jogger girl's grandma.
To steal the hand, Dean has to wear tux to a museum shindig as Bela's date. Upon sight of him she says, "You know when this is over, we should really have angry sex." Dean is at a loss for words at first and replies, "Don't objectify me." Good stuff. Dean is so Captain Kirk.
Dean's date is the desperate old cougar who is the grandma of the jogger chick that is killed early on. She's all over him. It's funny in a sad way. He should take one for the team and give the old hag a toss in the sack.
Bela steals the hand and sells it for money. As she is counting her fat stack, she sees the ghost ship. She runs to Sam and Dean for help. The ghost is going after people who have spilled their own family's blood; whether it was intentional or not. They cast a spell to get Bela off of the ghosts target. They conjured the ghosts brother; the person that sentenced him to death. The ghosts kill each other and Bela is saved. Instead of thanking them, she pays them 10K.
She never reveals which relative she killed or why.