On his 85th birthday, crime novelist Harlan Thrombey is found dead in his room with his throat slit. Just as authorities are about to dismiss the tragedy as suicide due to the lack of evidence to prove otherwise, Benoit Blanc arrives at the scene to conduct his own investigation. Soon, it is revealed that all of Thrombey's family have a reason to murder the family's patriarch. Now Marta, the dead man's caregiver and most trusted confidante, might be able to identify who the killer is.