Aalavandhan

Nandu suffers from paranoid schizophrenia and experiences severe delusions. When Vijay brings Teju to visit him at the asylum, Nandu's mind merges Teju's identity with his deceased stepmother Jayanthi, who abused him and his brother during childhood. His delusion convinces him that Teju is Jayanthi reincarnated, and he believes he must protect Vijay by eliminating this "threat."

Earlier in the film, doctors warn Vijay that Nandu could perceive people as figures from his traumatic past.

Nandu escaped the mental asylum after killing two inmates, Sulthan and Paasha, leaving no trace of his whereabouts. He overpowered them violently and slipped out without being detected. Later, he confronted his maternal uncle, who had been responsible for his institutionalization, and the uncle died from shock during the confrontation.

The doctors had warned Vijay that Nandu remained dangerous and capable of violence.

After meeting Sharmilee, a socialite, Nandu became obsessed with her. However, during a drug-induced moment, memories of Jayanthi's abuse flooded back, causing him to see Sharmilee as another incarnation of his stepmother. This triggered his violent breakdown, leading him to brutally murder her before burning her body to hide the evidence.

Nandu's pattern of seeing Jayanthi in women he encounters was established when he first mistook Teju for his stepmother.

Nandu's diary, discovered at the ancestral home in Ooty, revealed the family's dark history. It explained that their mother Priya committed suicide after discovering their father Santhosh's affair with Jayanthi, who subsequently became their stepmother. The diary also detailed the coin toss that decided the twins' fates: Vijay went to boarding school while Nandu remained trapped at home with the abusive Jayanthi.

The diary provides context for why both twins despised Jayanthi and why Nandu's mental state deteriorated so severely.

Priya, the twins' biological mother, learned about her husband Santhosh's affair with Jayanthi, their household help. The discovery drove her to suicide, leaving her young sons vulnerable. Jayanthi then became their stepmother and subjected both twins to severe abuse, which traumatized Nandu particularly deeply and contributed to his later mental illness.

The diary reveals this tragic event as the origin of the family's broken state.

When the twins were young, their family made a difficult decision about their upbringing through a coin toss. Vijay won and was sent to boarding school, away from the toxic household. Nandu lost and remained behind with Jayanthi, enduring years of physical and emotional abuse. This separation meant Nandu bore the full brunt of Jayanthi's cruelty while Vijay escaped to a healthier environment.

This explains why Nandu's psychological damage is far more severe than Vijay's.

During the final showdown in Ooty, Nandu overpowers Vijay and corners Teju. However, when Teju defends herself with a belt, it triggers traumatic memories of Jayanthi's punishments. Overwhelmed by visions of his mother pleading with him and the weight of his actions, Nandu apologizes to his brother and Teju. He then ignites gas cylinders in the room, causing a massive explosion that kills him and ends his torment.

The diary's revelations about their mother's death and Nandu's suffering foreshadow this moment of reckoning.

Nandu believes he is protecting Vijay from what he perceives as a threat. His delusion convinces him that Teju is Jayanthi, the stepmother who abused them both during childhood. From Nandu's warped perspective, he is eliminating a dangerous person to save his brother, not understanding that his perception is entirely false.

His paranoid delusions began manifesting during the asylum visit when he first mistook Teju for Jayanthi.

After escaping the asylum, Nandu tracked down his maternal uncle, who had played a role in having him confined to the mental institution. During their confrontation, the uncle died from shock and choking when Nandu revealed his presence. This violent act demonstrated how far Nandu was willing to go to confront those he held responsible for his suffering.

The uncle's involvement in Nandu's institutionalization was mentioned earlier in the film.

Nandu is diagnosed with paranoid schizophrenia, characterized by severe delusions and hallucinations. He experiences paranoid beliefs, such as perceiving his stepmother's identity in others, and visualizes his deceased mother. This condition developed from years of childhood abuse by Jayanthi, making him a dangerous individual who cannot distinguish between real threats and his traumatic memories.

Doctors warned Vijay that Nandu could perceive people as figures from his traumatic past.

Vijay and Teju retreat to Vijay's ancestral home in Ooty to escape Nandu's pursuit and the danger he poses. The remote location provides them with a temporary safe haven. While there, they discover Nandu's diary, which reveals the traumatic family history that shaped Nandu's psychological breakdown.

Nandu's threatening message at their home and the escalating danger forced them into hiding.

Months after Nandu's death, Teju reveals she is pregnant with twins. Concerned about the kind of childhood their children might have given the family's traumatic past, she worries the cycle of trauma might repeat. Vijay reassures her that their children will be raised in a loving, supportive environment, free from the shadows that plagued their own childhoods.

The film began with Teju's pregnancy news, creating a circular structure at the ending.