We live in a country where our guests are considered to be Gods a la ‘Athithi Devo Bhava’. But, when the same guests extend their stay endlessly, they tend to become a pain. GUEST IIN LONDON is nothing but a cinematic version of this saying. The film starts off with the flashback of events which mirrors the entry of an elderly man named Gangasharan Gandothra (Paresh Rawal) and his dutiful wife Guddi (Tanvi Azmi) in the lives of Kartik (Kartik Aaryan) and Anaya (Kriti Kharbanda). Both, Kartik and Anaya are on the verge of getting married for their individual vested interests. While Kartik wants a permanent citizenship in UK, UK citizen Anaya is getting married to him for the sake of money. Meanwhile Gangashara and Guddi land up in their house as uninvited guests and make this fake marriage of theirs into a grand celebration involving the neigbours from the locality. No sooner do they get married, Kartik and Anaya realise that they have actually fallen in love with each other. Gangasharan and Guddi’s love and affection towards the newly married couple only funnels their love for each other much more. As days pass by, Gangasharan and Guddi show no signs of going back to India. All the attempts to pack them back prove futile for Kartik and Anaya. One day, the world around Kartik and Anaya comes to a standstill, when they discover a startling truth about Gangasharan and Guddi. What is the shocking truth about Gangasharan and Guddi which Kartik and Anaya discover, are Gangasharan and Guddi as innocent as they appear or is there more than what meets the eye, is what forms the rest of the film.