All creatures are mysterious. A child with the kind of brain that doesn't allow for co-ordinated movement or communicative speech or gesture is more mysterious than most. Such a child is 10-year-old Josephine. Nicknamed Joe Egg by her parents – in blackly comic fashion, because she's always sitting around doing nothing – she is the eponymous subject of Peter Nichols's 1967 play. Back then, the critic Irving Wardle praised it for having "significantly shifted our boundaries of taste". What used to seem daringly new today feels heavy-handed.
Joe's parents – admirably presented by Rebecca Johnson and Ralf Little – are trying to cope with caring for her – and with other people's reactions to her. They jokily project conversations on to Joe and pretend she is engaging with them. They also act out little scenes for each other's benefit and, breaking through the fourth wall, directly address the audience. This music-hall quality (highlighted by an abundance of laugh-aloud funny lines) is exaggerated by Corin Buckeridge's breezy score and Simon Higlett's expressionistic Play School-meets-Monty Python set. Against this distorted background the adult characters shrink to cartoon dimensions; the situations come across like sugar-pilled public information broadcasts on disability and euthanasia issues.
By contrast, the only vibrantly real person in Stephen Unwin's production is Joe herself; her physical traits convincingly presented by Jessica Bastick-Vines. Here lies the power of play and production (joint between Liverpool and the Rose theatre, Kingston). For much of the time, Joe sits centre stage in her wheelchair, facing the auditorium. We look at her and we wonder – how would it feel to be her; what would it be like to be responsible for her? The questions are not glibly resolved.