Ivy and Isla Mercer are eleven years old when they leave a boy in the woods with his foot in a trap and walk home for dinner. They are not disturbed by what they have done. They are curious about it.

Over the next three decades — through the controlled experiments of high school, the calculated freedoms of Chicago, and the baroque violence of Paris and Barcelona — the twins refine what they are: two people of extraordinary intelligence with no interest in the moral weight of other people's suffering, and every interest in its architecture.

Detective Mara Langley has been following them since the fox den. Told in four parts across four decades, Twins is a psychological thriller that treats evil not as an aberration but as a method. Patient. Elegant. Philosophical. And always watching back.