Hariharan Pillai Happy Aanu movie is all about Hariharan Pillai (Mohanlal) who is a contractor and civil engineer to boot. His crew is Vasu (Jgathy) who is a carpenter, Velappan (Cochin Haneefa) who is supervisor and Sundaran (Salim Kumar) who is a painter. They all lead a happy life till one day Hariharan learns that Satyapalan was cheating him and had no intention of giving back the money he borrowed.Kavya (Jyothrmayi) who is daughter of Satyapalan. She falls in love with Hariharanpillai and helps him in getting his money back.

Muthu and his disabled sister live with their grandmother and uncle Suseelan. Muthu's life takes a turn when he falls in love with a woman and meets a mysterious man.

The story revolves around Saji and his friend Maya Sakkariya who are college-mates. They decide to try their luck in television serial production. As the shooting progresses, the two friends face the severest challenge of their lives.