Knock, and the door will be opened) is a 1966 Indian Tamil-language thriller film directed by J. P. Chandrababu.

Savitri Ganesh, K. R. Vijaya, Shoba (credited as Baby Mahalakshmi), Chandrababu and Manohar star, while A. V. M. Rajan, Cho and M. R. R. Vasu play supporting roles.

[5][6] Shankar murders his mistress, Geetha after finding out that she has had a child with another man.

Shankar meets his wife (the one that he had abandoned) Meenakshi, and his daughter and lives with them.

[9] Kalki praised the acting of actors, cinematography but felt songs did not stay in the mind and concluded saying we expected innovation and revolution in Chandrababu's film but got disappointed.