As a TV writer-director, John Morton specialises in the sort of English talk that either means nothing at all or something completely different from what was said. In the sitcoms Twenty Twelve, W1A and currently Twenty Twenty Six, the hesitations, repetitions and desperate metaphors – in conversations that sound improvised but are precisely written – reveal corporate conceit and deceit. But the stilted and stalled speech in Morton’s playwriting debut, Eclipse, represents unsaid and unsayable things among the gathered family of Edward, a late-stage cancer patient who has asked to die under “home hospice” care at an old rectory in Devon.

Edward, confined behind a door in the corner of the convincingly lived-in kitchen that dominates Simon Higlett’s set, is never seen or heard but feels completely real. That theatrical illusion recalls theatre’s genius of offstage characters, Alan Ayckbourn, as do many of those we see: bickering siblings Jonathan (Rupert Penry-Jones) and Sarah (Sarah Parish), diffident and assertive respectively, and the latter’s hapless, tactless husband, Graham (Paul Thornley). The pair of end-care nurses – gently attentive Karen (Selina Cadell) and self-consciously jolly Linda (Lizzie Hopley) – are also familiar English comedy types.

Ayckbourn has taken English middle-class domesticity into dark areas but Morton goes further, the laughs deliberately snuffed out as death advances. The final scenes feel like a sequel to David Eldridge’s End, also about a dying man, but which spared the audience the clinical terminus. A silent, bleak attention in the theatre acknowledges that theatregoers are either remembering or anticipating such horror.

Morton’s special contribution is the hyper-realistic speech – ums, stumbles, yesses that really mean no – placed like musical notes in apparently bland exchanges that sing with subtext. A five-page sequence about whether the stricken patient might eat a yoghurt and, if so, which flavour reveals deep family dynamics, medical psychology, suppressed emotions and another death suffered by one character.

In tight financial times, it’s impressive of Chichester to employ, in the Minerva studio theatre, 10 actors, four with one scene each. But this large cast is needed to represent the crowded house that a home of death can become. As a district nurse and the local GP, Katharine Bennett-Fox and Maanuv Thiara suggest the life behind their characters’ few necessarily expositional lines. Morton’s direction is as precise as his writing, a tiny glance at a watch having colossal impact in context. It was a risk that there might be no new theatrical life in death but Eclipse has found it.