Naagin 3 starts with Bela (Surbhi Jyoti) going to the haveli where Aghori Baba tells her that huge trouble is looming over entire Naag Lok and she as the Naag Rani has to protect it. She comes to know that Naagmani is stolen and is shocked. Guruji says we are searching for it, but we don’t know who has taken it. The story goes into a flashback where we see Bela as little Ruhi who is attending to her injured mother. Her mom says I have saved the Naag Mani from enemies but it is your responsibility to look after it now. She remembers how her mom said that Lord Shiva has entrusted them with the stone. Aghori Baba says it got stolen days before but I could only inform you today. He says tomorrow is Vishesh Chandra Grahan and you need to find it fast. He tells her to only bother about the stone now. The man blesses Bela with special powers where snakes bite her and she is infused with the severest of poisons.
He says your strength is huge now but your health will suffer. He says do not touch anyone now as that person can die. He says only your true life partner can escape this poison. Bela says my real love is no more, remembering Vikrant’s die. The Sehgal’s congratulate Rohit on the film. Sumitra (Rakshanda Khan) calls Bela and Maahir and he says she is in the washroom. Poulomi comes and says she is not there. Annu tells them that Bela just left the venue. She says Bela is in Andheri at a clinic. We are shown a flashback where Bela’s mom tells her that her grandmothers lost their lives saving the Naag Mani. She makes her promise to keep the stone safe as it is their dharma. Bela touches her mom’s picture and says she will fulfil her duties towards her clan. Baba comes to the body of a woman and says Ruhi should not come to know that her mother is still alive.
Upset Bela tells Vish (Anita Hassanandani) that she is unfit to be a queen of Naag Lok. Vish tells Bela to fulfil her revenge and tells her to be strong to save the Naag Mani. Bela says the stone is my priority now. The Sehgal’s come home and scold Bela for not informing them about her being unwell and going to the doctor. Maahir (Pearl V Puri) says she could have told him. Bela wonders who made up the story about her doctor’s visit.
Annu comes there and says she went to my friend’s clinic. Bela gets annoyed but agrees. Later, Annu informs Sumitra that her friend is a gynaec and asks why did she go there? Maahir attends to her bringing her water. Bela thinks of dismissing Maahir from there as Aghori Baba will come to her soon. Maahir and Bela have an argument and he leaves. Aghori Baba scolds her for being rude to Maahir and says you need your husband to reach the Naag Mani. She says you have to keep him happy but do not cross your limits. She asks Baba what needs to be done. He gives her a plan.
Ajitabh and police commissioner talk about the case. He says there is something wrong with the Sehgal’s family. He asks him what name have you given the case? Ajitabh says Agla Khoon Kausa. The commissioner asks about his partner. He says he is single. Vish walks in as Inspector Ramona and says she will assist him in the case. Ajitabh says you are too funny to be a cop.
Annu tells him that Yuvi has not disappeared but something terrible has happened. Vish enters their room and says she will keep a watch. The cop welcomes Vish on the case. At home, Bela cooks for Maahir and remembers Baba’s words that she has to feed him. She says I have made your favourite sabzi and requests him to eat. Maahir says I am not a toy that you will run me by a key. He asks her why is she punishing him? She requests him to eat. He is shocked to see her caring side. Sumitra calls everyone and says that Bela is pregnant. Maahir is shocked. Bela looks at Annu angrily. She understands that she wants to prove that Bela is a Naagin. In the police station, Vish is flirting with Ajitabh. She comes to know that they have put Yuvi’s phone under surveillance to find out where he is. Vish says he is in New Zealand. Ajitabh says how do you know?
In the room, Maahir comes flustered to Bela and asks if she is pregnant with Yuvi’s child. He says I will bring Yuvi back and he has deserted you when you’re preggers. Bela screams she is not pregnant. Maahir says I am not judging you. Bela says please trust me, I am not pregnant. Sumitra comes there and says the doctor has come home to inspect Bela. Annu tells the doctor to prove that she is a Naagin. Bela remembers Aghori Baba’s words that no person should touch her now as it can die. Maahir calls up Yuvi’s number and tells him to come back as Bela is pregnant. Vish gets shocked hearing this.
Maahir tells Yuvi that he will kill him for leaving Bela pregnant and running away. Vish gets worried. Ajitabh slanders Bela saying that she trapped an innocent man. Ajitabh says we will have to wait for Yuvi’s voice message. If that does not come, we will assume that Bela murdered him as he dumped her. He says I feel even Annu’s statement might be true that she is a Naagin. At home, the doctor says she wants to check Bela’s nerves but she stops her. Annu calls her up impatiently but the doctor says I am yet to check her up. Bela has an argument with the doctor when she tells her to open her eyes.
The noise from the sonography machine makes Bela very uncomfortable. She gets her scales. Bela prays to Lord Shiva for a solution. The doctor gets a message from Annu to click a pic of Bela in her Naagin avatar. Bela is in a huge fix about her situation.