Lysa Arryn
Catelyn's sister, widow of Jon Arryn, shut up in the impregnable Eyrie with her sickly son — nervous, possessive, and not entirely in her right mind.
A soul of House Arryn, born at Riverrun.
The fuller tale
Season One
Catelyn's sister, Jon Arryn's widow, and the reason half the plot is set in motion: it is her letter, written at Littlefinger's urging, that names the Lannisters for her husband's murder and sends Ned Stark looking in the wrong dangerous direction. At the Eyrie she is queen of her own small, locked kingdom — hostile to visitors, controlling of her son to a degree that unsettles even Catelyn, and quick to put Tyrion Lannister on trial for a killing he did not do. She will not send Vale swords south for anyone's war, and no argument moves her on it.
Season Four
Married to Littlefinger at last, and terrified of losing him the moment she has him — a fear that only sharpens when he arrives at the Eyrie with Sansa Stark in tow, calling her his niece and treating her with a tenderness Lysa has spent years waiting for herself. She corners Sansa at the Moon Door ready to throw her through it, certain of an affair that exists mostly in her own dread. Littlefinger talks her back from the edge with the gentlest voice she has heard from him in years, and then puts her through the door himself, telling her — accurately, for once — that he has only ever loved one woman, and it was never her.
How it ends for them
On the screen. Fell from the Eyrie (S4·E7)
The Lady of the Vale confessed she'd poisoned her own husband at Littlefinger's word, and threatened Sansa at the Moon Door in a jealous fury. Petyr calmed her, kissed her once — 'I have only loved one woman' — and pushed her through it.
On the page. Out the Moon Door (ASOS, ch. 81)
She confessed everything at the Moon Door with her hands on Sansa's back — the poisoned husband, the lying letter, all of it done for Petyr. Littlefinger pried her loose gently, said 'only Cat,' and pushed.
She dies at the Moon Door she loved to feed. In the show it comes moments after she has watched Petyr kiss Sansa in the snow: she drags her niece to the open door, raving, until Petyr talks her gently back — and then tells her he has only ever loved one woman, her sister, and pushes her through. In the books the scene runs the same course at greater length, Lysa confessing the poisoning of Jon Arryn and the lying letter in front of the one witness who matters, before Petyr pries her fingers loose with a single word — “only Cat” — and lets the sky have her.
Either way, the man she killed for was the man who killed her, and her death is the story’s first full confession: everything the realm believed about the war’s beginning was authored by the two people standing at that door. Only Sansa hears it, which is the point — from that moment the girl knows exactly what her protector is.
Their chapters, book by book
A Game of Thrones 2 chapters that name them
A Storm of Swords 3 chapters that name them
Where the page and the screen part
The bones of her story match across the tellings, but the books supply the childhood that explains her — the tansy, the forced marriage, the aborted child, all confessed in her final raving at the Moon Door — where the show sketches the obsession and lets the history stay dim. The aftermath differs too: in the books Littlefinger frames the singer Marillion for her death and extracts a confession, while the show has him talk his way past the Vale lords with Sansa’s tearful, calculated testimony as his shield. Book-Lysa is also a shade more dangerous — her jealousy of Sansa turns physical at the Moon Door itself, snow swirling into the hall while she screams the whole conspiracy aloud.
Their journey
Where the two tellings send them to the same place the road runs whole; where they part, the screen keeps the left and the books the right.