In the middle of the night) is a 1970 Indian Tamil-language crime thriller film, directed and produced by S. Balachander.

[2] Dhayanandam is a rich old man living in a sole home on an island with his mentally-ill wife Ponni and a few servants.

Dhayanandam is still extremely mad at his siblings for treating him badly in the past because he married Ponni, a woman from a lower caste.

Remaining guests start blaming Ponni, Dhayanandham and Saravanan and want to leave the island, which does not have any means to communicate with the outside world.

The next night, Ragini sees a mysterious man who looks like Dr. Saravanan from behind, push her dad Jambu with his wheel chair down the stairs.

Rest of the family is all relieved that the killer is dead, when the Doctor appears at the top of the stairs, surprising everyone.

Nadu Iravil was eventually released in 1970 and became a major success, prompting several distributors who earlier rejected the film, to return and beg Balachander for distributing it.

[3] The Indian Express wrote, "The movie succeeds as a very good entertainer entirely due to the directorial work of S. Balachander and Reddi's camera".