Maharani Season 4 opens in 2012 as PM Sudhakar Joshi's coalition nears collapse after losing West Bengal CM's support. Joshi's aide seeks Bihar CM Rani Bharti's backing, but she refuses. As Rani asserts her leadership in Bihar, Joshi allies with her jailed rival, Naveen Kumar, to undermine her. Soon, a commission report implicates Rani in an old murder case, triggering a CBI probe. The episode ends with a charged face-off between Rani and Joshi, setting the stage for a fierce political war.

Rani Bharti resigns as Bihar's CM after rejecting the Maheshwari Commission's allegations, declaring she will take her fight to Delhi. Her son Jai's growing ambition clashes with the old guard of Rani's party like S N Mishra and Kaveri. Meanwhile, Joshi manipulates Tamil Nadu CM Sunderraja to not switch sides and remain in his coalition. CBI arrives in Patna to arrest Rani, but she secures anticipatory bail. The episode ends dramatically as Rani names Roshni Bharti the new CM.

There is heavy backlash over Rani Bharti's decision to appoint her daughter as Bihar's CM. Party veterans like Kaveri and Mishra openly question the move, accusing Rani of promoting dynasty politics. As PM Joshi runs a social media campaign called #NangaNepotism against Rani and Roshni, tensions rise. Roshni soon faces funding cuts from the Centre, testing her leadership. In a fiery Assembly speech, she boldly challenges PM Joshi proving, she's more than just Rani Bharti's daughter.

The political storm deepens as PM Joshi targets Rani Bharti's family through a coal-mining deal linked to her son Jai. While Rani seeks alliances in Tamil Nadu to counter Joshi, he cunningly manipulates Kaveri - sending her to the UN. Distrust brews within Rani's camp as Jai clashes with Roshni over his business ties with Rishi Agarwal, and Kaveri begins doubting Rani's motives. When Kalanaag warns that Kaveri's betrayal is imminent, Rani is forced to choose between loyalty and survival.

Kaveri represents India with a powerful UN speech as Rani and Roshni tighten control in Bihar, cancelling all Akshanta Group contracts tied to Jai. This sparks a family confrontation, leading Rani to placate an angry Jai and enlist him for Delhi's political battle. PM Joshi counters Rani's growing alliance against him by framing CM Sunderraja's family in a scandal. As Rani unveils her new opposition front - Rashtriya Jan Sammaan Morcha - Joshi's sabotage forces Sunderraja to leave her coalition.

The personal and political turmoil in Rani Bharti's world deepens. Jai seeks Aditi's hand, but Balmukund's acceptance comes with a secret condition that could shake Bihar's power structure. As Rani tries to unite allies, Kaveri warns her that Jai is entangled in a coal scam. Kalanaag manipulates Mishra and fuels divisions within Rani's circle. Just as Rani begins to steady her ground, the CED arrests Jai from his own engagement, and PM Joshi dissolves Parliament, calling early elections.

Jai is forcibly brought to Delhi by CED for questioning over alleged money laundering linked to coal block deals. Despite harsh custody conditions, he resists pressure to admit to the charges. Meanwhile, Rani and Roshni uncover Skyron corruption, tracing illicit payments to Nachiket. Jai is granted bail, and Rani nominated him as a candidate in the upcoming elections. Jai exposes Joshi's financial scandals publicly and reveals that Nachiket is the illegitimate son of PM Joshi.

Election results end in a hung parliament, plunging Delhi into chaos. Rani prepares to stake claim for power, but betrayal brews within - Kaveri and Mishra rebel, splitting the RJSP. Meanwhile, Jai's secret dealings spiral into tragedy, shaking Rani's world to its core. As Joshi triumphantly returns as Prime Minister, Roshni is arrested, and Bihar slips from Rani's grasp. In a searing final confrontation, a shattered Rani vows vengeance, promising to uncover the truth at any cost.