What is a ghost? Is it a spectre? A phantom? That shadow in the corner of your eye?
The figure at the end of your bed? The breath on the back of your neck?
Or do we carry them with us? In our deepest thoughts? Our wildest imaginations? Our darkest memories?
These are the questions that sisters Annabel and Miriam Chester will be forced to answer.
With tensions between the pair fraying, and their late father's vicious nurse Alice prowling the grounds intent on vengeance, one answer will become terrifyingly clear: their ghosts are very real.

* Snake in the Grass by Alan Ayckbourn runs until Saturday July 4.

The word "love" issues repeatedly from millions of televisions as Wimbledon fortnight rolls on. In tennis terms it means . . . well, nothing. And there is nothing by way of love in this, one of Alan Ayckbourn's ventures into the supernatural 'chiller', as it unpicks the lives of two sisters reunited by the death of an abusive father.
A tennis court harbours his haunting presence for Annabel Chester, the older of the two, just back from many years in Australia to claim her inheritance. It's not long before the ghostly echo of balls crashing into wire netting stir horrible memories of being used as "human target practice" by a man who turned even an innocent summer game into a form of cruelty. No wonder she could never watch Wimbledon.
Fleeing to the other side of the world has evidently brought her no relief. Yes, she had some success in business but, as so often happens, the product of an abused childhood found a violent man to marry. Small wonder that she became an alcoholic.
She's off the booze back in England, unlike her sister Miriam who is rarely without a wine bottle in hand. Sexual abuse by the same father has turned her into a self-confessed "mess".
As the story unfolds, however, she becomes outwardly stronger and more calculating. Yet ultimately she, too, remains haunted by the ghosts of the past. Nicol Cortese manages to convey this combination of calculation and vulnerability with some panache. Nicole Firth, meanwhile, garners something that would have seemed impossible in the play's early scenes - sympathy for Annabel as her haughty, prickly and brittle exterior begins to crumble and reveal the ruin within.
Jan Nightingale is convincingly menacing as the father's former nurse and Debra Relton-Elves's taut direction brings the play to a startling conclusion after a riveting second half. Simon Sharpe's set, fronted by cracked pots full of weeds and wilted plants, captures the sense of decay in what should be a lovely English garden in high summer. Even the background birdsong sounds like Macbeth's crow making "wing to the rooky wood".
No chirpiness here. Not a lot of laughs either for those more used to Ayckbourn's rib-ticklers. What there is, not for the first time with this master playwright, is considerable sympathy for abused women. In that respect, the Criterion has done him proud.

Chris Arnot