In his 2011 book Rewriting the Nation: British Theatre Today, Aleks Sierz describes a new trend on the contemporary British stage. Taking place in what he calls ‘rival realities’, the plays written during the ‘quantum decade’ of the 2000s were ‘rich in visions, imaginations and fantasy’, as if they had ‘taken a mind-expanding drug, encouraging us to go beyond the normal confines of daily life’ . As an example of this theatre which ‘creates different realities, […] explores imaginative worlds [and] ascends to heaven or stumbles into hell’, this paper will look at Nick Payne’s 2012 play Constellations. One in a few number of recent works for the stage which resort to quantum tropes as a poetic means to conjure up the hidden reality of subjective experience, Constellations explores the ‘rival realities’ mentioned by Sierz around the main character of Marianne, a quantum scientist who suffers from a brain tumour and whose relation to the world is therefore gradually altered. As her love story with Roland, a beekeeper, develops, her descriptions of quantum physics provide meaningful images to evoke the woman’s declining cognitive abilities and her disturbed inner world, where the main drama both does and does not take place, stuck in the repetitions and variations of the play’s fragmented and nonlinear structure. By comparing Marianne’s distorted perception of and engagement with reality with the spooky nature of the world portrayed by the Multiverse theory, the story can no longer be located in time and space: imaginary possibilities, contradictory scenarios, parallel developments, and unresolved options proliferate and unfold before the spectator’s eyes. This unconventional exploration of the protagonists’ possible options, choices and life paths converges with the ‘Many-Worlds’ counter-intuitive approach to reality and dramatises key quantum principles such as probability, uncertainty, complementarity, non-locality, superposition, and entanglement. These scientific concepts become aesthetic and ethical principles, characterising both Payne’s ‘theatre of possibilities’ and Marianne’s mental space and undecisiveness. Questioning our sense of inner and outer reality, Constellations eventually creates a dramatic space which allows for a subversive form of theatrical realism to develop, based on what can be called a ‘quantum psychopoetics’ of the stage. Indeed, with physical uncertainty being a necessary concept to describe a reality which is fundamentally plural – as the probabilistic model of quantum physics suggests – while psychological indeterminacy characterises the nature of our minds, the play questions our relation to the world in a way which revolutionises what ‘taking place’ means. Using Jean-Pierre Sarrazac’s study of modern theatre through the prism of the notion of possibility, Claude Régy’s work on staging the ‘state of uncertainty’ of the world and the subject, and Élisabeth Angel-Perez’s analyses of the ‘spectropoetics of the stage’ developed by some recent British plays, this paper attempts to define and situate a theatre no longer ‘in-yer-face’ but ‘in-yer-head’. In this kind of theatre, the two meanings of the word ‘occurrence’ – as ‘that which happens’ and ‘that which comes to mind’ – are no longer distinct. it aims to show that ‘giving place’, rather than ‘taking place’, characterises Payne’s drama, as it splits into a multiple series of possible dramatic developments instead of providing a single thread of definite and exclusive actions. This expansion informs the postmodern poetics of a play concerned with building a storyworld where events give way to probabilities, allowing the protagonist to explore the power and limits of free will.