A scientist (Arya) in the year 2065 invents a time machine and to prove its capability sends it back in time to 2015. However, the machine is seen by three persons in the past — Elango (Vishnu Vishal, solid), a young man who is finding it hard to catch a break, his friend Pulivetti Arumugam (Karunakaran, whose quips keep you in splits), a pretend astrologer, and Giridhara Parthasarathy (TM Karthik, equal part crazy and funny), a inventor. The three are involved in a minor accident and they witness the time machine appearing out of thin air while they are recovering from the shock. While Parthasarathy plans to keep it to himself, he ends up in a coma and Elango and Arumugam use the machine to further the latter's astrology business. They recover things that have been lost by people by going back in time but do so under the guise of astrology. However, during one such excursion into the past, they meddle more than necessary and this prevents the death of Kuzhandaivelu (Ravi Shankar), a gangster and extortionist, who is actually tragetting Rajarathinam (Jayaprakash), the father of Elango's girlfriend Anu (Mia George). Soon, things begin to spiral out of control and their lives become living hell.

Time travel movies can be a lot of fun and that is something that debutant director Ravikumar seems to have realized straightaway. There is a lot of humour in Indru Netru Naalai, and much of it comes out organically — the comedy scenes are very much part of the plot. That is why the early trips that Elango and Arumugam take in the time machine have a touch of humour about them. After hearing on the news that gold prices have shot up, the two friends journey back in time to the pre-Independence era, pick up a lot of jewellery and when they pay the jeweller in modern-day currency, he returns it to them saying, "Velinaattu kaasu ellaam naan vaangarathilla." It is only then that it strikes them that contemporary currency will not have any value in the past.

This is something that we must have all, at one point or the other, fantasized about — how we could become super rich if we could go back in time and invest in things when they were cheaper. It is such relatable moments that make the film and the concept easily accessible to us. Time travel movies can easily become a mindbenders but here, there is always clarity in the screenplay — though, sometimes, at the cost of brevity. And these moments are really fascinating; in one song, Elango takes Anu through moments from her childhood and at one point, she ends up kissing herself when she was a newborn baby! Yes, it is a slightly illogical moment but it is also a deeply touching one. The scene in which Elango, Arumugam and Parthasarathy chance upon the time machine is presented in thrilling fashion. And the fact that the friends decide to use Arumugam's profession as a camouflage to use the machine (in one cheeky scene, a person requests them to find the missing Malaysian airplane!) and make money is a masterstroke — that rare instance when astrology is actually science. And, the visual effects are not tacky and we readily suspend our disbelief during the time travel scenes.

But in the second half, the wonder of time travel is used to tell a cliched gangster tale. The whole episode where Elango and Rajarathinam seek the help of Kuzhandaivelu's mentor and rival feels unnecessary given how little impact it has on the plot. The film is also a little short on energy — yes, we laugh at the jokes, wonder at the science and care for the characters but the narrative lacks pep in places making the film a tad overlong.