In the final decade of the 19th century, mysterious widow, Hester Appleyard, arrives in Australia, haunted by a secret past. Here, in the new world, she establishes a successful school for young ladies. But six years later, on Valentine's Day, 1900, the enigmatic headmistress allows her pupils to picnic at Hanging Rock. And there, in the strange brooding landscape, something unthinkable happens.

Hester's three star pupils and a governess have disappeared. Led by a dogged Sergeant, local men search for the missing. Has something supernatural befallen them? Or has a human outrage occurred? An aristocratic young Englishman, Michael Fitzhubert, was the last person to see the girls, and when the search is abandoned, he is compelled to return to the Rock where he makes a shocking discovery.

The missing Rothschild heiress has been found claiming to remember nothing. Rumours spread and the sergeant turns his attention to the college. His investigation intensifies Hester's paranoia and she grows certain that the young orphan, Sara, knows something about the disappearance.

Hester struggles to contain the hysteria as aftershocks from the disappearance disrupt the old order. A mysterious visitor summons memories of Hester's dark past, while Sara seeks escape from the college. The story of the missing girls in the months leading up to the picnic is revealed.

The French governess grows increasingly suspicious of Mrs Appleyard's erratic behaviour, and fears the worst when she is told that Sara was unexpectedly collected by her guardian. As Mademoiselle searches for answers, the Sergeant travels to Melbourne to seek a last interview with Irma, and a secret vow made by the missing girls is revealed.

Hester has grown increasingly certain that her vengeful husband is behind the disappearances and is coming after her. As she prepares to flee, the arrival of Sara's guardian provides conclusive proof of Mrs Appleyard's lies. As Hester travels to the Hanging Rock, we finally learn all that led to her demise, the haunted past she ran from, and the secret lives of the missing college girls.