Terre Haute is a tightly-scripted, compelling drama about this year's favourite subject, terrorism. The difference is that despite the CIA's efforts to prove otherwise, the perpetrator was a lone American with no affiliations to any subversive organisation, either at home or further east.
The two-hander sees orange-jumpsuited, young Harrison (Arthur Darvill making an impressive professional stage debut) appearing in a cage to meet veteran Peter Eyre as fading writer James who has come to interview him.
These are extremely thinly veiled disguises. Harrison's bombing took place in Oklahoma City in April 1995 and therefore he must be Timothy McVeigh, while his penpal, "the most prolific writer of my generation" specialising in historical novels, has to be Gore Vidal.
Their meeting is fascinating because, despite the ex-marine mass murderer's extreme and often misguided views, he is clearly intelligent with "a highly original mind".
For a little over an hour the old man interviews the younger, teasing out his history and views on life, eventually asking the critical question as to how and why he chose to set off a massive bomb that killed 168 men, women and children.
Edmund White's script, well directed by George Perrin, also reveals a surprising amount about the life and methodology of the writer and this gives a balance and authenticity.
Terre Haute is recommended as one of the Fringe's most thoughtful plays with masterful acting from the veteran and a passionate effort from his tyro colleague.