THE EFFECT of Gamma Rays on Man-in-the Moon Marigolds is the strange title of Paul Zindel’s Pulitzer Prize and Obie winning play.

There is justification for the name in an experiment which Tillie, the younger of two sisters, whose shyness conceals her high intelligence, is pursuing.

In the experiment she sees how gamma radiation from cobalt-60 affects marigolds, sometimes transforming them into strange flowers completely unlike the originals.

It’s unusual for geniuses to come from deprived backgrounds.

Tillie and her older sister, Ruth, an epileptic, are dragged up by a single alcoholic mother in a deprived area of Staten Island.

The emphasis of this fascinating play is on the interaction of the three women.

Ruth is brimming with confidence despite her condition. Robyn Elizabeth Henshaw plays her as an easygoing, flirtatious teenager and her portrayal of her character’s epileptic fit is utterly convincing.

Megan Relph who is Tillie, puts across a far more introverted character. Yet she is no push-over and is dedicated to her work despite coming from such a non-academic family.

The actors who play the sisters are to be praised both for their character representation and their relationship with one another.

The sisters are not helped by the immature behaviour of their mother, Beatrice. Kathryn Fennell plays her just right grasping her insecurity and, later portraying utter frustration.

The ending has different outcomes for different characters, but I won’t spill the beans.

This gem of a play, directed by Mark Edgar-Clarkson making his directional debut at the Garrick, seems tailor-made for the cast.

* The Effect of Gamma Rays on Man-in-the Moon Marigolds. Is at the Garrick’s Lauriston Studio until Tuesday, October 30. For tickets, telephone 0161 928 1677 or visit Garrick website. Star rating: * * * * *