The Argus: Brighton Festival Fringe launches today

Gary Mepsted’s psycho-sexual comedy drama about the twisted consequences of an affair comes with a warning that it is only suitable for over-18s. But it isn’t as grown-up as it thinks.

The title refers to a physics phenomenon whereby the interference of two or more waves produces a new pattern. Here, this is a loose metaphor for the warped family unit that emerges when second-rate actor Bruce and his sexually frustrated wife Ruth (June Harris) bring younger actress Saffron (Lucy Shaw) into their home and bed.

Director Robert Holden raises a few laughs skewering the couple’s snobbery, from Ruth’s exasperation at the hired help to Bruce’s pricked pride at being stuck in regional theatre. A set littered with photos of him none-too-subtly emphasises his utter self-absorption.

But jarring tonal shifts and a basic lack of believability squander a potentially interesting premise. Ruth and Saffron’s obsession with Paul Bentinck’s bumbling, ineffectual Bruce makes little sense other than as a requirement of the plot.

The indiscriminate use of the C-word and focus on bodily fluids is clumsy rather than provocative and soon becomes tiresome. Mainly spoken by Ruth and Saffron, such sex talk serves only to highlight how thinly written and two-dimensional they are – the desperate housewife and the nymphomaniac.

The cast (including a suitably twitchy Josh Varty as Bruce and Ruth’s troubled son Simon) do their best. But this play isn’t nuanced enough for a proper exploration of sex as a substitute for affection and lacks the black wit to give us something compellingly grotesque.