Last year, Wednesday by Ian Winterton was one of my picks of the Fringe. This year, Shred Productions return with Sherica, his next script, and though it lacks some of the previous production's compelling focus, its place is still assured on the top shelf of fringe new writing. On the strength of these two shows, his main theme appears to be man's inhumanity to man (and woman). But whereas Wednesday was an unflinching and tightly-focused three-hander, a single-shot dispatch from a horrific crime scene, Sherica takes a more panoramic view of a complex moral minefield. The setting is a northern academy school, previously fee-paying, now full of bussed-in troubled youth and right at the front-line of the class war. Well-meaning teacher Mr Feather is juggling compassionate discipline for new pupil Natalie with sleeping with her prostitute sister – he prefers 'sex worker', as any Guardian-reader would. Semantic and political discomfort combine in a seething stew of liberal paranoia. The play, like Wednesday, ends in the inevitable continuation of a cycle; this inescapable social repetition seems to obsess Winterton as it does David Simon, creator of TV's The Wire; another author unwilling to give in to audiences' desire for an easy answer.As with Shred's last outing, there will probably be many people who see this show and leave unsettled by the absence of a redemptive shaft of sunlight – but as Natalie ripostes after having been scolded for calling a classmate a 'posh c**t', 'there's always need for language like that'; and, by extension, for plays like this. Writers capable of addressing complex social issues are easily stigmatised by those who prefer to look away; which is a shame, because Sherica has great performances, such a pace that it occasionally ought to breathe more (scene changes seem oddly abrupt in the Vault's harsh light), and a savage sense of humour. I want this play to do very well indeed, and though it might go unnoticed in the tide of 'dark' and 'disturbing' new writing, I sincerely hope that that won't be the case.