Is it a coincidence that zombies are out in force this Fringe, as a pandemic sweeps the globe? Probably, but the thought of sharing moist, hot air with a bunch of people who recently visited a portaloo certainly adds extra bite to a show such as Subsist (**), which is set more than a year after the undead took over.

JD Henshaw's play is no gorefest, but rather an exploration of the psychological consequences for those fighting to survive, or thinking about giving up, after all of their loved ones have succumbed.

Four strangers have been thrown together in a house, long after the time for normal human interaction has past. It's hard to believe that this quartet would have survived for so long without following some basic ground rules, and it's disappointing to see a textbook error resulting in a grisly denouement.

This may not happen in every performance, as the cast choose an ending seconds before the show begins. It's a neat concept, but one that is stronger than either the script or performances.

Opening Night of the Living Dead (****) is a much more light-hearted affair, and if the title appeals, the show will delight, given that it delivers exactly what it promises and does so at a breakneck pace, with spot-on comic timing and a great deal of flair. There's always a danger that shows fitting this profile - snappy title, tiny venue, post-pub timeslot - will be cobbled-together affairs, but writer Joshua Dickinson has woven plenty of smart lines into his very, very silly tale about a production of Romeo and Juliet going from bad to worse. He's also rather adorable as its love-struck techie hero.

Director Miles Barden makes a virtue of the small stage by having cast members and marauding zombies dash across it to well-chosen songs by Kaiser Chiefs and The Automatic, although at times things get a little too close for comfort - on review night a rather nasty neck injury sustained by Romeo left several in the front row sprayed with blood.

"Stick to one-star shows to avoid mass panic" is one of the tips offered by the host of How To Survive A Zombie Apocalypse (*), presumably conscious of the fact that he and his castmates don't really have a show at all.

Their spoof seminar is listed under comedy but they've neglected to prepare any jokes; they seem to expect a barrage of questions from the audience to inspire the bulk of the material but panic when required to improvise. It would have been easy to at least throw in a few cheap scares - when performers disappear for no good reason and when everyone is asked to close their eyes it feels like the apocalypse must be imminent, but all that follows is more patchy advice, punctuated with awkward pauses.

What's most disappointing is that the cast don't even seem particularly enthusiastic about their own subject matter, and break the spell completely by acknowledging that their collective expertise is the result of watching films.

Subsist, Sweet Grassmarket, until August 23. Opening Night of the Living Dead, C cubed, until August 31. How to Survive a Zombie Apocalypse, Zoo Southside, until August 31. SHONA CRAVEN If the contemporary secular equivalent of John Milton's epic poem Paradise Lost is a bourgeois middle-aged businessman knocking off his east European au pair in her seedy London bedsit while his fragrant wife is looking the other way, then the world is in considerably more trouble than is already obvious.

Yet remarkably that's exactly the premise of The Fall of Man (**), Jonathan Holloway's new piece for his scaled-down Red Shift company, which cuts up some of the crucial bits of Milton's original with the squalid and not terribly dangerous liaison between Peter and Veronica.

What we're left with over a slight 40 minutes is a curiously pointless affair, where the fruit of the original sin soon turns sour in the seedy Eden the pair create for themselves.

Performers Stephanie Day and Graeme Rose do what they can in the appropriately cramped stage set-up, displaying total commitment to the piece.

The situation is simply mundane. However commonplace the mid-life crisis scenario, to put it on a higher plane and invest it with some kind of spiritual significance is at best seriously misguided. Or if you are going to indulge such a concept, at least let it lead to some kind of enlightenment.

As it is, the only believable line is when Veronica calls Peter a dirty old man before the whole thing fizzles out and into the void.

In Oh My Green Soapbox (***), performer/director Lucy Foster charts the unearthed relationship between the preservation of the polar bear and one-night stands in a playful eco-fable about the often all too personal motivations behind political activism.

Foster does this through a pick and mix of low-key confessional, adventure playground style constructions and video footage that resembles altogether friendlier out-takes from Dom Joly's brand of comedy terrorism.

Improbable Theatre associate director Foster is charming in her delivery, which builds an arctic landscape from little more than a sheet and the soapbox of the title. At the moment it needs more meat on what is a wry and wilfully small show. Then again, that might be enough, and maybe by filming herself on the streets dressed in a polar bear suit that actually looks like a mouse she has a host of eligible bachelors swooning at her furry paws.

To echo a line from those halcyon days of single-issue sloganeering that might just be making a comeback, the personal is political. Oh, My Green Soapbox might not offer any great profundities to change the world - yet - but it might just end up melting a few hearts enough to prove that protest can be cuddly, serious fun.

Things get a whole lot more frightening in Funny (***), writer Tim Nunn and director Katherine Morley's latest collaboration for their Reeling & Writhing company.

Inspired by a confidential document that suggested humour could be used as a weapon while interrogating Middle Eastern subjects who applied meditation as a defence mechanism, Funny applies the possible outcome of such a tactic to current conflicts.

It opens with Tommy Mullins' Paul doing a stand-up routine based around a series of war stories. It transpires that Paul is being taught by Keith MacPherson's real-life comic Jack, and the stories are first-hand. When Paul receives a call from Donald Pirie's Steve, the trio end up on the next flight to the Middle East.

Paul and Steve aren't squaddie cannon-fodder, but are serious operatives on a mission. Paul has also been taking yoga classes, and is now in a place where all his anger is channelled with a Zenned-out deliberation, even if he does happen to be wearing clown feet while wielding a gun.

With an opening that resembles Trevor Griffiths' play, Comedians, Nunn's script is making some serious observations, and the action is delivered with all the Boy's Own urgency of a 24-style covert operation. As Jack becomes the unwitting victim of Steve's legitimised torture campaign, another form of brainwashing has taken hold of Paul.

The naturalistic scenes are broken by a series of physical routines from Mullins that applies a variety of comic techniques with fresh menaces. Beyond these diversions, Funny is a prime time political thriller. It would be fascinating to hear what real-life stand-ups might think of how humour is hijacked and subverted in a play where the phrase "This one'll kill ya" is the ultimate one-liner.

Where the punchline is, however, is anybody's guess.

The Fall of Man, Pleasance, until August 30. Oh, My Green Soapbox, Pleasance, until August 31. Funny, Assembly@7 Holyrood Road until August 30. Neil Cooper