Catherine's brother, Matthew, has leukaeimia and the struggle of their family to reacting to such tragedy is viewed through her eyes.
With its windswept exteriors and focus upon the claustrophobic existence of a family unit, it's perhaps inevitable that The Darkest Light will draw comparisons to The War Zone (1999), although the themes here are terminal illness and faith, as opposed to dark secrets and sexuality.
The Darkest Light is set in the farmland of the Yorkshire Dales, as largely seen through the eyes of ten year-old Catherine, whose eight year-old brother Matthew is suffering from leukaemia (both children brilliantly portrayed by newcomers Arnold and Walton). Their mother Sue (Fox) is realistic but trying to suppress her natural feelings in order to appear strong; father Tom (Dillane) is a mess of tangled emotions, as best evidenced in a powerful scene in which Matthew becomes hysterical upon discovering his hair is falling out, and father and son shave each other's heads in the barn with sheep clippers.
Meanwhile, Catherine has befriended a new Hindu girl at school, Uma (Kavita Sungha), and on the moorland, where low-flying military aircraft roar above head, the two experience a flash of blinding white light that the former interprets as a a divine sign that her brother will get better. As this news spreads, a fevered mood grows, which is intensified by the outbreak of foot and mouth disease in the family's livestock.
However, as a film tackling the murky area of faith in crisis, The Darkest Light, though not lacking in atmosphere or emotional depth, fails because its ultimate outlook and use of harrowing imagery - piles of burning cattle, one terminally ill little boy being put through the agony of a bone marrow transplant - is resoundingly bleak and distracts from any spiritual message it tries to convey.
Though the film doesn't lack emotional depth or atmosphere, it is simply too bleak to communicate the personal, spiritual message it attempts to convey.