Setting amateur sleuth Father Brown the task of solving a baffling case, in which the killer seems to be invisible, suggested that John Goodrum had come up with a gripping whodunnit based on the classic mysteries by GK Chesterton.

Unfortunately, an overlong first act, in which the details of the case take an age to explain, creates a ponderous pace.

And the fact there are only three characters in addition to Father Brown, means the murderer is not too hard to fathom.

Goodrum takes on too much in writing, co-directing with David Gilbrook, designing and acting in this Rumpus Theatre production.

It could have benefited from someone else making cuts to add tension to his clever plot and 'invisibility' ploy.

Ella Hope (Anna Mitcham) has received a threatening letter from her ex-fiance, demanding she gives him the fifth knife of a priceless, antique set.

Ella's aunt (Karen Henson) seeks the help of Father Brown.

John Lyons, best known as DS Toolan in A Touch of Frost, plays Father Brown with less charm but greater authority than Mark Williams.

He shares some good scenes with Henson's astute aunt and Mitcham's frightened niece as the pace quickens in the second act.

Three stars