|Sam and Dean are worried about Bobby, as he struggles with his grief over Rufus' death. Sam finds a series of unusual deaths among related people in Pennsylvania, but Bobby isn't interested and tells them to leave him alone. As they pack up Dean's Mustang, they're worried about Bobby, but take comfort in knowing Ellen will be home soon. Ellen gets home to Bobby - she's been hunting with Jo for a week. She commiserates with Bobby over Rufus' death and fusses about his drinking. Bobby grudgingly accepts her care and Ellen teases that it's why he married her.
Sam and Dean check out the scene of one of the deaths and find no clues other than a thread of pure gold on the ground. As Sam checks out genealogy records, Dean visits another of the relatives who's still living - Shawn Russo - but all they learn is that the victims' ancestors arrived in America in 1912. Travel agent Anne Witting is busy at work selling holidays to Cuba when time freezes, and a blonde woman appears and places Amy's car keys under the photocopier. When time starts again, Anne looks for her keys, and when she goes to retrieve them her scarf is caught in the copier and strangles her. After Anne dies, the blonde woman reappears with a book in her arms. She opens it on a list of names, and a thread of gold falls from the bookmark. She then crosses Anne Witting's name out and leaves.
After the brothers investigate the scene, Dean calls Ellen, who reports that there have been 75 similar deaths nationwide. They all appear to be freak accidents and gold threads have been found at the scenes. Jo and her crew is looking into a cluster of deaths in California, and the only common factor they've found between the victims is that their forebears all arrived in 1912 on the Titanic, a passenger steamship that none of them have heard of. After further investigation, Sam finds that on its maiden journey across the Atlantic, the Titanic nearly hit an iceberg. Disaster was averted, however, by the first mate - the suspiciously named I.P. Freely. He finds a photo of the crew, and I.P. Freely is revealed to be the angel Balthazar.
The brothers summon Balthazar, who claims that he went back to time to stop the Titanic from sinking because he hated the movie "Titanic" and the song "My Heart Will Go On." When Sam asks how he could change history, Balthazar states that there are no more rules. Aside from all the passengers he saved whose descendants would never have been born, he acknowledges some other changes - Sam and Dean don't drive an Impala, and Ellen and Jo are alive. When Sam and Dean point out that something is killing the descendents of the Titanic passengers, about 50,000 people, Balthazar states he doesn't care and disappears.
The boys call Bobby, who has worked out that the Fates are responsible. Apparently, they're trying to counter the changes Balthazar's actions bought about. Bobby suggests they convince Balthazar to re-sink the Titanic, but when Dean reveals that Ellen and Jo would die, Bobby tells them to do everything they can to not let that happen.
The next day Sam and Dean try to speak to Shawn Russo, but he gets hit by a bus and killed. Sam notices a woman watching from a nearby building, and, thinking that she could be Fate, they pursue her. They're standing in a dark kitchen when she stops time and opens all the gas valves in the room. When time restarts, Dean's flashlight dies, and he takes out his lighter. When it sparks, the gas ignites.
But Castiel appears at the last second and transports the boys to safety. He tells them that Fate is angry at them because, in averting the Apocalypse, they rendered her obsolete. Then, by "dangling themselves in front of her," Dean and Sam made her even more angry, and Castiel says that she likely won't stop until they're dead. They will need to kill her using a weapon Balthzar has, and Sam suggests that they use themselves as bait.
As Ellen tells Bobby, Jo has tracked another 30 deaths on the west coast. Ellen suggests they need the angels to sink the boat, so Bobby reveals that she and Jo's lives are at stake, as well. Ellen, however, decides that this is acceptable.
Back in Chester, Sam and Dean try and go about their business - anxious at the possibility of death at every turn. Finally, a piece of machinery falls from a building, but Castiel stops time before it crushes them.
The blonde woman appears and confronts Castiel. She is Atropos - one of the three Fates - and she is angry that fate no longer has a role and that everything is in chaos since the Apocalypse was averted. She also charges that Castiel ordered Balthazar to avert the Titanic disaster so that there would be 50,000 souls in existence that otherwise wouldn't be, and intimates this is part of his war effort.
Castiel doesn't admit anything, but she says she will kill Sam and Dean if Castiel doesn't sink the ship. Changing the future is one thing, but changing the past in the last straw. Castiel in turn threatens to kill her, and she reminds him that she has two very powerful sisters who will go after Sam and Dean if she dies. Just as Balthazar is about to kill her, Castiel stops him and agrees to sink the Titanic again.
Sam and Dean wake up in the Impala back at Bobby's place, with Celine Dion's "My Heart Will Go On" playing on the radio. They both think they have had the same dream, but Cas appears and reveals that what happened was real. He wants them to remember so they know who Fate is, and so that they know Castiel is fighting for freedom from destiny. Then, when Dean asks, he tells him that Balthazar really did change history because he didn't like the movie "Titanic," revealing nothing about his possible war plans.
Inside, Bobby lies asleep on the couch. Sam and Dean look at him sadly, knowing what he's lost. Dean covers him with a blanket and they let him sleep.