Haunted 3D: Echoes of the Past follows Devadutt Choudhary, aka Dev (Mimoh Chakraborty), a successful filmmaker eagerly awaiting the release of his latest film, Laila Majnu. His world comes crashing down when he discovers that Sonali (Aradhna), the film's leading lady and the woman he loves, has been unfaithful with its male star. Heartbroken, Dev leaves Mumbai without a word, accompanied only by his cousin, Titu (Gaurav Bajpai). Their journey leads them to the tranquil hill station of Maniktal, where Dev decides to rent the mysterious Maniktal Palace. However, the grand estate harbours dark secrets. While one wing of the palace remains accessible, the other has been sealed off for decades, its keys long lost, according to caretaker Trilok (Hemant Pandey). Yet on his very first night, Dev is awakened by unsettling noises and discovers the supposedly locked wing standing eerily open. Venturing inside, he encounters a malevolent spirit tormenting a young woman named Sunheri (Chetna Pande). As Dev tries to protect her, he is baffled by the revelation that Sunheri appears to belong to another era altogether. Drawn into a chilling mystery that transcends time, Dev must uncover the truth behind the palace's haunted past before its sinister forces consume them all. What unfolds next forms the heart of this supernatural thriller.