Through These Lines, written by first-time director Cheryl Ward, is the story of Sister Florence Whiting, a World War I army nurse.

The tunnels within Mosman’s Headland Park, which straddles the ridgeline along Middle Head Peninsula, provide an evocative site for theatre. As Cheryl Ward says, the venue is almost a character itself.

These old military tunnels were excavated in 1870 to defend Sydney from coastal attack and now provide a new underground theatre.

We are led five metres below ground to a former ammunition store. It is dark and damp but sets the scene perfectly.

With the assistance of lanterns, a lap-top operated by Engie Ho, projecting images and a wartime soundscape, we follow this young Australian nurse as she leaves on a troop ship to Cairo and then to the Western Front.

The play is made up from real-life recollections researched from diaries and letters housed in the Australian War Memorial.

The six-member cast tells the stories of nurses, soldiers and doctors. and of their experiences. The radiant spirit with which they undertake the logistical and expressive challenges bring about many poignant performances.

The small roles are all well handled, even those that suffer from the sentimentality imposed on them by some parts of the story.

Mairead Berne as Sister Mary Douglas and numerous other nursing staff is animated and energetic and illuminates the shadowy space.

The key figure of Sister Florence Whiting is superbly played by Coraline Bywater who manages to portray decency and kindness in a living hell, giving the play much of its muscle.

Indeed all the performances are excellent from this fine ensemble, who recreate vivid social realism. Johann Walraven coveys the essential loneliness of Lieutenant Roland Davies and invests the role with just the correct credence.

What is excellent about this play is the way it explores this historical period through individual lives and the motives that drive people on, and in the process addresses a number of stark truths about the horror of war.

It is directed by Cheryl Ward with a mix of narrative whose speed which sometimes slows due to the need to chronicle historical events and the limitations of the performance space. It is very confined and the many entrances and exits do become repetitious.

However, the play is staged with simple ingenuity which effectively evokes the scarred emptiness of the wartime landscape. This is never going to have the impact of a full production and it doesn’t claim to. Instead, with a dressing-up box and a great timely account of war, it is testimony to how much you can do with these components and just how far they can take you creatively.

In the space of 90 minutes it gives an effective summation of the story, which is clear-headed and unsentimental, and captures both the pain and pity of war — something that still defies understanding.