Investigation: The Beginning

Akash Sakthivel is a happy and loving middle-class employee working in a workshop of his brother's friend Karan in Ambasamudhram.

He has a loving sister-in-law Durga and brother Chandra, who is ready to do anything for him. He is an advocate in the District Court of Tirunelveli.

Akash Shakthivel's marriage is arranged with Jessica George after making peaceful talks with his brother Joseph who was initially against their marriage due to the difference of religion. Akash's close friend Arun Kanthavel is a police officer in CID and a close friend from his childhood and he has come to meet him.

All was going well until Jessica is kidnapped mysteriously and then being, killed mysteriously. This shatters Akash and Jessica's brother, who requests Akash to get justice for her death if he loves her truly, which he accepts gladly.

Later, an ID card holding Akash as a CID officer is accidentally taken by his sister-in-law and upon being confronted by her, he reveals to her about the trip that he had gone to Dehradun before 3 years.

He had lied to his brother he goes to Dehradun for a trip but goes there for being trained as an IPS officer in CID where Arun has also come for training. Akash is posted as an officer undercover to observe Karan, his brother's friend but, a criminal in illegal activities despite having a workshop and his brother becomes shocked after hearing Akash's job since he also works with Karan's brother as an advocate who is, in turn, a political activist.

Keerthika is a girl from a rich background whose only world is her family and she has an elder sister and a younger sister. Her elder sister works as an Agent in the Detective department while Keerthika works as a successful surgeon in her father's hospital.

Later, Keerthika's father Dinakaran is investigated by Akash about Jessica's murder since she was working in his lab as a microbiologist. But, he refuses to tell any clues and instead requests for protection to his family due to the interrogation made by his department. He accepts his request and gives tight security to his house and hospital. Akash also officially takes charge as ACP of Tirunelveli to investigate the case by himself further.

Keerthika and Akash have a misunderstanding initially when he worked in the workshop of Karan. But, they become good friends later. Now, Akash has to face many hurdles from ACP Fernando George, a crime branch police officer working under Karan's payroll, causes troubles to Akash while he was investigating Jessica's death that angers Akash. However, he remains silent as he has to obey Fernando due to his in charge of the case.

But, Unfortunately, the case is shifted to Akash and Arun officially by the CID citing the inefficiency of the police department lead by Fernando. Akash manages to get a clue from Jessi's brother about her visit to Cambodia before a month and goes with Arun to find a clue about the case. They learn about a lady in Cambodia close to Jessica and goes to meet her.

The lady's name is Caroline, a close friend of Jessica. After completing MBBS, Caro shifted to Cambodia while Jessica continued her job in India. Caroline further tells about a call that she had received from Jessica one day and she had heard some sounds of chasing after which she got feared and informed to the boss of Jessica, Keerthika's father.

But, Caroline is killed by an unknown assassin immediately after her confession while Akash and Arun get injured fatally who are then shifted to Keerthi's hospital for treatment in Tirunelveli, and Akash is taken care of by Keerthi in the hospital.

After Akash recovers, Keerthi's father tells him the actual incident that happened in Jessica's death after feeling bad to see Akash's condition. Jessica was a successful microbiologist in his hospital. Despite being a microbiologist, she has a helping tendency towards people. One such incident with her behavior had completely shattered her life. She gathered evidence against Vikram and Co. after being requested by a journalist who learned of her bravery and helping attitude towards people. The journalist intends to expose Vikram's illegal weapons and his involvement in selling cocaine exported by Pakistani terrorists which will paralyze peoples and causes an indirect reaction in their normal life.

Despite the opposition and warnings from Keerthika's father to stop her investigation, she started her investigation under the guidance of the journalist and collects evidence against Vikram's activities and plans that he had made for the next 10 years to destroy India.

The evidence is given to Fernando, who takes Jessica to Vikram while keeps the evidence with himself for destroying it in the future completely. Later, Dinakaran witnessed Vikram killing Jessica brutally and rushes from the place in fear.

After learning the truths from Dinakar, Akash's brother starts to plead Akash to come out of this investigation fearing for his arrest and also for the sake of his brother's welfare. Everyone turns against Akash, including Keerthika, who fears that his life will be posed under threat due to the further investigation that he undergoes in the case of Jessica.

Only Arun supports Akash in his investigation and he challenges Akash's brother that they will finish the case within 10 days. Akash further tells his brother that he already knows about his profession as a lawyer in Vikram's company when he was an undercover officer and also accuses him of saving injustice while he himself, speaking about justice.

Feeling bad and guilty, Akash's brother realizes his mistakes after being sidelined by Durga who also scolds him for being a criminal lawyer. Chandra gives full support to Akash and asks him to bring Vikram to Justice even if it means to pose as dangerous to him. Keerthika's father then, asks Akash to marry Keerthika as he should have a life partner and also for the sake of Keerthika, who had now fallen in love with Akash and is waiting for his arrival after finishing the case.

Akash accepts his proposal happily and says to him that, "he also had fallen in love with Keerthika after seeing her care for him but, first, he wants to get justice for Jessica's death and then think about Keerthika" but he gives him an assurance that he will marry Keerthi after finishing the case of Jessica's death. Dinakar happily accepts his request and also pleads him not to live Vikram and also fuels up Akash not to live any of those criminals who pose a threat to the nation's welfare, which is accepted by Akash gladly.

Vikram learns that Chandra has reformed and in a fit of rage, he sends his henchman to kill Chandra and Durga including the twin daughter Sri Vidhya while Kavya escapes and takes shelter in Akash's house. Their house is set on with fire thus, killing the trio. Akash gets shattered completely after learning his brother's death but, is persuaded by Keerthika to be calm.

Fernando feels bad after seeing the brutality of Vikram and fearing that he also will be betrayed by Vikram one day, he turns up against him and reforms into a good cop and also joins hand with Arun and Akash to give full support for their mission to expose Akash. As a part of his duty to support Akash, Fernando hands off the pen drive to Akash which contains all the evidence against Vikram being indulged in his illegal activities and collaboration with Pakistan to destroy India.

However, Vikram has kidnapped Keerthika and her family. He threatens Akash to hand over the evidence in the islands of Covalam beach in Tiruvananthapuram. Akash goes to Vikram's hideout after exposing his atrocities to the media that is unknown to Vikram and saves Keerthi's family. In an ensuing fight, Arun and Fernando get killed.

Akash is beaten up badly by Vikram and tells him how he killed Jessica by brutally plunging her into the water. He further says his brother's death through a fire where he died slowly from the fire. Akash becomes furious after hearing it and paralyzes Vikram by beating with a sharp chain in Vikram's spine.

Akash also sets the hideout of Vikram with bombs and destroys it completely so that no one can hide on that island anymore.

He also says: "It was a punishment for him as he has killed Jessica and spoiled the lives of so many peoples." Vikram is given life-long imprisonment citing the strong evidence that was submitted by Akash.

Later, Akash performs cremation for Arun and also salutes at him while Joseph, Jessica's brother, asks him to marry Keerthika who has been waiting for him and he further appreciates Akash for getting justice for Jessica's death. While Akash and Keerthika reconcile, Joseph goes back to take care of his parents and a younger sister who needs financial support through Joseph's help and it was the one which he and Jessica had wished.

Akash marries Keerthika with a grand reception arranged by her father and seeks the blessings of Keerthi's father while he also sees a reflection of Jessica smiling to him with happiness with his brother and his family blessing him happily. Akash and Keerthika go to Pune for a honeymoon trip and also surprises Keerthi that he has come to Pune for another Investigation. He sees Arun's photo and says to him, "Investigation to be continued." While he also assumes like Arun is laughing at him for his quotation. However, Arun really laughs at him for the quotation who has now appeared as a reflection of Akash.

Later, Akash and Keerthika spends some happy moments and Akash shows a symbol of success to his friend Arun and he quickly disappears thus, ending happily for a temporary period until Akash starts off the Investigation which has been assigned for him by his superior officer.