Claire Randall, a nurse, lives in Scotland with her husband, Frank, after the end of World War II. They're trying to rebuild their marriage after the war, while Frank studies his family tree, including a big-bad ancestor Jonathan "Black Jack" Randall. Pro tip: Anyone named Black Jack shouldn't be trusted.
One day, Claire and Frank watch a group of women dance around the nearby stone circle of Craigh na Dun. The next morning, Claire goes to collect some plants (she's a budding botanist... pun intended), and the stones scream.
Claire almost passes out, and when she wakes up, she finds herself in the middle of a scuffle... with old-school rifles and axes and men in kilts. She runs smack into Frank... but it turns out he's not Frank. He's a man saying he's Jonathan Randall. Say what?
A band of Scotsmen in kilts takes Claire away. One of their men, named Jamie, is injured, and Claire uses her nursing skills to treat him, even though the men don't understand words like "antibiotic" and pronounce surgeon as "chirurgeon" (3.91).
After Claire heals Jamie, the men take her to Castle Leoch, where she meets the clan chieftain, Colum, and his brother, Dougal. Snooping in Colum's journal, she realizes she's in the year 1743. Yikes. The chieftain and his brother agree to keep her at the castle, even though they suspect she's a spy for the English.
Claire spends her days at the castle helping Mrs. FitzGibbons, the female jack-of-all-trades, and becoming the surgeon (or should we still say chirurgeon?) in residence, taking over for the doctor who has died. She heals people, and gets to know that strapping young injured lad, Jamie, better.
Claire tries to escape a few times, like during the busy Gathering at the castle, but never succeeds. One day, Dougal decides to take her and Jamie with him on the road. He's collecting rents from tenants, and plans to make a pit stop along the way at a nearby fortress to see if he can figure out just who the heck Claire is.
The captain of the fortress is, of course, Jonathan Randall. He and Claire fight, no one knows who she is, and her life is pretty much in danger. In order to keep her from falling into Randall's hands, Dougal arranges for Claire to marry Jamie, a.k.a. James Fraser, which would make her Scottish instead of British.
She agrees, not that she has a choice, and goes through with the ceremony. To make it official, they have to consummate the relationship. Hey, Jamie is hot and pretty sweet, so why not? Claire takes his virginity and maybe, just maybe, they start falling in love.
Still, Claire is two hundred years in the past. When she has an opportunity to make a run for the border (in this case, Craigh na Dun instead of Taco Bell) she takes it. Unfortunately, she gets kidnapped by—guess who?—Jonathan Randall.
Jamie risks life and limb to rescue her. Because she put his life and the lives of his men in danger by disobeying him, he decides he has to punish her. He whips her with a belt... and kind of likes doing it. Claire is mad at being whipped, but she eventually comes to understand why he did and tells Jamie she loves him. (Psst… don't try this at home, okay?)
They return to Leoch, but Jamie has to leave on a long hunting trip with the Duke of Sandringham. While he is gone, Claire gets a message that Geillis Duncan, a woman suspected of being a witch in a nearby village, is ill and needs Claire's help. Claire gets to Cranesmuir and finds out it's a trick. Laoghaire, a girl who is jealous that Claire got to marry Jamie, lured her there and turned Geillis in to witch hunters. Laoghaire is also probably jealous that Claire's name doesn't look like it's pronounced leg hair. Just sayin'…
Both Claire and Geillis are almost burned at the stake, but Jamie rescues Claire at the last minute; Geillis, however, isn't so lucky. Before she is taken away, Claire notices something: Geillis's smallpox vaccination scar. Yep, she's another time traveler.
Jamie and Claire flee to Jamie's estate of Lallybroch for safety. There, Claire meets Jamie's sister, Jenny, and her husband, Ian. The reunion is cut short when, shortly after Jenny gives birth, Jamie is captured by English dragoons. Claire goes to rescue him with the help of his friend Murtagh.
He's being held by—who else?—Jonathan Randall in Wentworth Prison. Claire sneaks in and finds Jamie in terrible shape—bruised, bloody, and with a broken hand—but she can't get him out before Randall shows up. To save Claire, Jamie agrees to let Randall rape him. Randall tosses Claire out of the prison, where she is almost devoured by wolves; she kills one, and a man named MacRannoch kills the rest of the pack and gives her shelter in his cabin.
MacRannoch is a friend of the Frasers and helps rescue Jamie. Randall is presumed dead after the jailbreak. Claire nurses Jamie back to health, then travels with him to an Abbey in France to continue his recovery.
There, Jamie is so sick that the priests perform last rites. He is also so damaged by Randall's rape that he doesn't want to have sex with Claire anymore. That just won't do, so Claire chats it up with Brother Anselm who tells her to sit in the rectory and let an answer come to her.
Here's the answer: impersonate Jonathan Randall, making Jamie so mad that he attacks her and has sex with her. Well that's dark. She does it, he does it, and they do it, and the whole thing works, and Jamie is miraculously better the next day. Later, they descend to the hot springs deep beneath the abbey. It's very womblike, and to complete this symbolism, Claire tells Jamie she is pregnant. The end.