Spiced with upbeat humour, this action comedy starts with Ashoka Varma (Prathapachandran) a police officer, trying to prevent smuggling and drugs exporters. On the night he found the crucial evidence needed, he was murdered in his house. To find the murderer Kerala Home Minister (Oduvil Unnikrishnan) invites C.I.D. Ramdas aka Dasan (Mohanlal) and C.I.D. Vijayan (Sreenivasan) to Kerala.
On the day they arrived, CI (Azeez) takes them to their residence. They mistake Damu (Mala Aravindan) their cook for the murderer and beat him up. Due to Damu's injury they took their supper in a hotel. In that hotel Ramdas overhears a conversation and mistakes Isaac (N._L._Balakrishnan) and Prof. Vidyadharan (Paravoor Bharathan), two bird watchers, as the murderers.
After the supper, Dasan and Vijayan walk along through streets and run into Isaac. When they try follow him, they are shot at and ambushed by a group of villains and a fight breaks out. After the fight they are saved by Prabhakaran Thampi (Karamana Janardanan Nair), the real smuggler and drug king, who pretends to be mill owner involved in a lot of social service projects. Prabhakaran Thampi advices Dasan and Vijayan to withdraw from the investigation telling that there are many officers, who were investigating this case, have been murdered and that he does not want the duo to share their fare. Dasan and Vijayan are frightened but they put on a brave face before him.
Dasan and Vijayan decide to go undercover and start the investigation. With the help of Vijayan's idea they dress up as Moopla umbrella repair men. While investigating, a lady (K.P.A.C. Lalitha) gives them an umbrella to repair. They try to ask her about Isaac but she is not interested. They do a bad job in repairing the umbrella. At that time the lady's daughter-in-law Shobha (Ambika) arrives there and she spots Vijayan's fake beard and realizes that they are not genuine repair men. Thinking that they are burglars, the women raise an and neighbours gather to catch the "burglars". The duo run away from there, leaving behind their repair kit.
After that failure, Vijayan and Dasan dress up as Tamil parrot Tarot diviners, based on Dasan's idea. When they reach a bus station, and Shoha too is there. She recognises them and alerts the other passengers that they are thieves. The local people get hold of the duo, and beat them up and take them to the police station. The CI (Azeez) reaches there and informs the local people that the duo are CID's from Tamil Nadu. When the duo leave the police station, Shobha apologises to them, and Ramdas accepts the apology..
After that day Ramdas arrives at Shobha's house and gives them a new umbrella as a replacement for the one he broke. Shobha gives him tea, but at that time he sees Isaac and runs after him, without drinking tea. He follows Isaac and finds his abode.
In the DIG's office, Dasan and Vijayan tell the officers that they have found the murderer and they will arrest him with all necessary proof. When they come out of the DIG's office they meet up with Prabhakaran Thampi who has come there to invite DIG for the stone-laying ceremony for a hospital. Thampi enquires about the investigation. The duo tell him that they are close to catching the culprits, who are masquerading as pillars of the society (referring to Isaac) and that they will unmask them. This frightens Prabhakaran Thampi.
That night, when they return from the cinema, they are attacked by a masked man (Thampi's sidekick) in their house acting on the behest of Prabhakaran Thampi. They fight with him and takes his mask from his face and one of his shoes, but he manages to escape from there.
The next day Ramdas and Vijayan goes to Isaac's house. Vijayan dresses up and acts as a servant named Thankappan in front of Isaac, hoping to take his blood. But Issac does not allows him anywhere near the house. So Ramdas advises him to get employment in another house as servant and in the night to sneak and take the blood of Isaac after knocking him out with chloroform. The neighboring house happens to be Prabhakaran Thampi's house. When Prabhakaran Thampi arrives at house, he does not recognize Vijayan, because of the disguise.
Ramdas visits Shobha and apologises for running away from their house the previous time. Shobha's mother in law(K.P.A.C. Lalitha) tells him that her son was murdered in an accident. Dasan asks Shobha about this. She tells him that her husband Rajendran was murdered in a hit-and-run accident at checkpost. However, she did not get any compensatory "drying-in-harness" job, because Rajendran died two days before completing the mandatory 2 years. He promises her that he will do his best to help her.
Meanwhile at Thampi's house, Vijayan is caught in a power struggle between Thampi's wife and mother. Thampi's maid falls for Vijan, who is annoyed by that. At night, Vijayan sneaks to get Isaac's blood but accidentally, inhales chloroform while sneezing.
At midnight, a mysterious figure arrives at Prabhakaran Thampi's house. Prabhakaran Thampi realizes that he is his old friend Anandan Nambiar (Thilakan). Years ago, acting together, Nambiar and Thampi had stolen some money from a Marwadi businessman and had invested their shares in crime and had thus become mafia dons. Nambiar had broken out from jail and wants Thampi's help to escape. Next morning, Prabhakaran Thampi reads the news about Anandan Nambiar and gets worried about this compromising him. Anandan Nambiar requests Prabhakaran Thampi to get him a fake passport. Prabhakaran Thampi tells him it won't be easy and suggest Anandan Nambiar to hide in his copra godown.
Thampi's household maid servant continues to set her cap at Vijayan and flirts with him. Prabhakaran Thampi tells him to give his friend a lift in his bicycle and take him to the copra godown. Prabhakaran Thampi's mother (Philomina) sees a disguised Anandan Nambiar and Prabhakaran Thampi introduces him as Ibrahim Kutty to his mother. Vijayan takes Anandan Nambiar to the godown. Both Vijayan and Nambiar speak in falsettos, and have doubts that they have met before, but both of them dismiss their doubts.
Dasan arrives at Prabhakaran Thampi's house. Prabhakaran Thampi is frightened to see him but welcomes him. They go to the upstairs. Dasan notices Isaac and begin to watch him. At that time, Vijayan arrives there with tea. He also tries to look, but ends up dropping the tea. The tea falls over Prabhakaran Thampi who beats him.
Vijayan comes back from Prabhakaran Thampi's house, finds someone wearing the mask of murderer and beats him. Then Dasan comes and catches Vijayan and saves Damu who had been wearing the mask. Damu criticizes them for not finding any proof for the investigation. Vijayan shouts at Dasan for his lack of support at Prabhakaran Thampi's house. Vijayan tells Ramdas that he is going back to Madras (Chennai). Ramdas reveals to Vijayan that Anandan Nambiar broken out from jail and is searching for them.
At that time, the phone rings and CI tells them that Home minister is waiting for them. They arrives at guest house. The Home minister asks them about their developments in the investigation. They tell him that they are observing the suspect from a distance. The Home minister criticizes them for not having carried out a proper investigation and threatens to have them cashiered should they will fail. Ramdas retorts to the Home minister that he has also got a bone to pick about the treatment of SI Rajan following his accident and reluctance of Govt. to give job to his widow Shobha. He suggests that Home minister should first try to get her job and then criticize the investigation.
They leave there in a huff. Ramdas relates to Shobha all that has happened. Vijayan doubts Dasan and teases that he fallen for Shobha. Dasan retaliates by taunting Vijayan for failing to obtain Isaac's blood. Ramdas challenges Vijayan and states that that he will bring Isaac's blood without his help.
Dasan arrives at a hotel where Isaac (N._L._Balakrishnan) and Prof. Vidyadharan (Paravoor Bharathan) who has gone for lunch. Dasan tries to get Isaac's blood using a syringe, but manage to get only the waiter. Isaac tries to catch him but he escapes from there. Isaac recognizes Dasan, who has been following. He suspects that he came to stole his experimental details of bird watching.
Prabhakaran Thampi arrives at copra go-down and tells his man to start the drug running from Idukki. His lorry rams down a check post gate and the police chase them.
Meanwhile, Dasan tries to draw Isaac's blood when he is engaged in bird watching. Isaac beats Dasan and chases him but he escapes in his Jeep. At that time Prabhakaran Thampi's lorry comes that way, Isaac jumps into the lorry and beats Prabhakaran Thampi's men, throw them out and follows Ramdas. Dasan's jeep gets damaged and he sees Prabhakaran Thampi's lorry and tries to stop it. When he gets into lorry, Isaac beats him but Dasan manages to escape because Issac is distracted by the sound of the bull finch that he has been studying. The police arrive there and are under the impression that Dasan has single-handedly overpowered the goons and seized the ganja shipment. Realizing what is going on, Dasan acts the part.
Prabhakaran Thampi shocked to hear the news about the seizure of his shipment and blames Anandan Nambiar for all this. Prabhakaran Thampi's man tells Nambiar that there is another way go to Dubai without a passport. He introduces Gafoorka (Mamukkoya) to him, who, for a sum, is willing to redirect his cargo ship sailing to California via Dubai. Gafoorka advises Nambiar dress up as an Arab and teaches him a few basic Arabic greetings.
Isaac and Prof. Vidyadharan plan to go after the elusive bull-finch which was observed in an island and by chance, their boarding point is exactly where Gafoorka plans to rendezvous with Nambiar. Dasan and Vijayan who follow Issac and Viyadharan, sees them getting on a boat and looks for the nearest boat which happens to be Gafoorka's. On seeing his nemeses approaching, Nambiar jumps in the lagoon and escapes. Dasan and Vijayan catch Gafoorka and retrieve the money that they had been tricked into paying him, in the previous film.
Anandan Nambiar informs Prabhakaran Thampi the same CIDs who destroyed his mafia are the ones following him. Prabhakaran Thampi blames Nambiar and asks his man Kunjukrishnan to smuggle Nambiar away from Kerala. He suggests to spirit Nambiar away in lorry.
Ramdas requests Shobha to sign application for her job. Nambiar shocked to see the driver of lorry, meant to take him away, was Puthanpurakkal Balan (Innocent). He relates this to Prabhakaran Thampi and adds that Balan is a spy of CIDs. Prabhakaran Thampi decides to punish Balan who is dragged off the road by Prabhakaran Thampi's goons, beaten up and kidnapped and presented by Kunjukrishnan before Nambiar. Balan mistakes Nambiar for a Swami. Nambiar threatens him for being a spu. Balan understands what's going on. Nambiar orders Balan to kill Dasan and Vijayan and threatens to kill his family should he disobey. Balan goes to Dasan and Vijayan's home and Damu fights with him. He rescued by Dasan and tells Vijayan that he will stay with them.
Prabhakaran Thampi and Anandan Nambiar in the house. Nambiar sees Isaac watching through binocular. He frightens Prabhakaran Thampi and tells him that he is Also a CID spy. Prabhakaran Thampi says he is a poor man who started living some days before. Nambiar reminds Prabhakaran Thampi that one who caught his ghanja lorry who has baldness and fat. This frightens Prabhakaran Thampi and goes to watch him. He also misunderstood Issac as CID spy. Isaac has a suit case. Prabhakaran Thampi and Nambiar decides to catch it misunderstood as it is evidence against them.
At night Balan tries to kill Dasan and Vijayan while they are sleeping. But he couldn't do that. Dasan finds it and shocks. Vijayan wakes up and tells Dasan that he already told him that Balan is mad. Balan tells them, if he couldn't kill them then he will loose his family, that Anandan Nambiar threatened him. Dasan and Vijayan shocked to hear the news of Nambiar. They realizes that Namiar is there. Balan tells them about the baldness man. He thinks as Kunjukrishnan but Dasan thinks as Isaac. Dasan and Vijayan decides to rescue Balans family.
Next morning Kunjukrishnan takes away the suit case from Isaac's hand. Isaac and Prof. Vidyadharan chases him. Dasan and Vijayan along with Balan also chases them. They reaches at Prabhakaran Thampi's coconut farm go-down. Vijayan and Balan recognizes the place. While Isaac tries to rescue the Suit case and Dasan and Vijayan tries to beat Isaac. Dasan and Vijayan realizes that Prabhakaran Thampi and Anandan Nambiar are friends and there begins a fight. Balan tells Dasan and Vijayan that Isaac is not the baldness man who threatened him. Dasan and Vijayan asks Isaac who he is. He says that he is a bird watcher. After that they begin fight together against Kunjukrishnan and gang. Vijayan informs the police. CI arrives there with the police. Dasan and Vijayan find gold biscuits from go-down. Prabhakaran Thampi, Anandan Nambiar and their gang get arrested.
Dasan arrives at Shobha's house and gives her the appointment letter of her job. The Home Minister thanks Ramdas and Vijayan for their hard work for find the culprits and saving his seat. Ramdas also apologises to Isaac for misunderstanding him. Isaac says he doesn't mind because it was all for a good cause. After that Dasan and Vijayan leave to Tamil Nadu.
