This article focuses on the fraught questions surrounding replicas and their use in heritage contexts, drawing on an in-depth qualitative study of a historic replica, the 1970 concrete St John's Cross, Iona. We examine how replicas 'work' and unravel the part that social relations, place, and materiality play in the production and negotiation of their authenticity. The research shows that replicas are important objects in their own right, acquiring value, authenticity, and aura. The 'life' of a replica generates networks of relationships between people, places, and things, including the original historic object. While the underlying human stories of creativity, skill, and craftsmanship are rendered invisible when replicas are treated as mere surrogates, we argue that these 'lifestories' should be incorporated into future conservation, management and interpretation. The article spells out practical advice and guidance for heritage professionals who find themselves dealing with replicas.