In 1996, a treasure-hunter and his crew search the wreck of the RMS Titanic for an infamous blue diamond known as the Heart of the Ocean. Instead they discover a drawing of a naked young woman wearing the stone around her neck -- and it's dated the day the ship sank to the bottom of the sea. A nationwide search reveals the young woman's identity as Rose Dawson, now one hundred and one years old, whose past contains the last remaining clues to the diamond's location.
In 1912 Rose is only seventeen, with a fiance and a first-class ticket for the maiden voyage of the world's fastest, most modern, and truly unsinkable ship. Bound for America, Rose is not sure she wants to survive the trip: she's being forced to marry to secure her family's fortunes, and despairs at a life of rigid upper-class values and an even more rigidly controlling husband. His engagement present is the legendary Heart of the Ocean, but it might as well be an iron shackle around her neck.
As she's about to throw herself into the Atlantic, Rose is saved by Jack, one of the ship's third-class passengers. A young artist determined to make his own way in the world, Jack won his ticket in a poker game and left the continent with nothing but the clothes on his back and a dream of a better life. Jack can't understand why a girl like Rose, who has everything he lacks, would want to throw it all away. As circumstances conspire to bring the two of them together, again and again, they realize they share a connection that transcends differences in wealth, experience, and even class.
But fate is hurtling toward the young lovers as quickly as the Titanic cuts through the icy ocean waters. Even if they manage to escape Rose's violent fiance, they can't avoid the iceberg ahead. For the first time in over eighty years, Rose is about to confess the secrets of that terrible night: a story of passion more precious than any jewel, and of a love that would -- like the ship that brought them together -- go down in history.
At [x-thousand] words, TITANIC is a work of romantic historical fiction with a sprawling cast of characters, including both imaginary and very real passengers such as Captain Edward John Smith, shipbuilder Thomas Andrews, and the "Unsinkable" Molly Brown.
... yeah, okay, please don't poke fun at me for pounding something out real quick.
But! Does this begin to help? Titanic is a movie and not a book, which makes this a bit trickier -- we introduce what's at stake first because of the movie's framing device, where usually I would say to put them after the introduction of the main character.
But the essentials are there. Character: Rose, suicidal despite being so young and privileged, which is an intriguing juxtaposition. This is no ordinary romance heroine, as her dashing and wealthy prince is equivalent to a jailer, and the historical realities for women in this period are NOT glossed over.
Main conflict: Rose falls in love with someone not her fiance! We get a brief description of Jack so that we can see what would make him so attractive to Rose, and also why it's not as simple as canceling her engagement. (He's poor, from a different class, they really never should have been allowed to meet, etc.) This heightens the basic conflict, and makes it about more than just loathing Cal.
And then there's the stakes. Again, because it's a movie they come a little bit out of order, but they're there. Rose and Jack might be discovered by her fiance, who is... not a nice guy, and might do them harm. Plus the ship is definitely going to sink, so we don't know if Jack survived. Maybe he didn't. Maybe Rose married the dude she hated. Those are the worst-case scenarios. Best case is that Jack and Rose might have been living blissfully together ever since the ship sank (although the foreshadowing makes that doubtful) and maybe even got rich off a stolen diamond.
It leaves out A LOT. But a query is supposed to! It's only supposed to contain enough to make people want to know more. So the very basic, central premise is laid out, with just enough tantalizing specifics and interesting details to make someone wonder: how did these totally opposite people fall in love? what happened to Jack? what happened to the diamond? has Rose's life since been a happy one? (It's been a long enough one, don't you hope she's been happy?) Plus there's a brief nod at the end to all the other characters whose stories might be connected to Rose and Jack's. So no one reading the query is confused about what the story contains -- again, on a very basic level -- and they hopefully are interested in knowing MORE. Hopefully enough to request more pages, or the full manuscript.
Was that helpful? This was a fun exercise, btw -- I've seen a few agents actually recommend trying to write your favorite books or movies as if you were querying them, to get a sense of how to focus in on the spine of a story and present it simply. So maybe you should try it yourself with some other titles. Or this one, if you don't think I did it justice.