The Berkendael Institute, Brussels, 1913. After nurses check on sleeping children and turn out the light, two get up and fight a mock battle. Running into another room, one hides behind Nurse Edith Cavell's voluminous skirts. She advises the other to search more thoroughly.

After war is declared, Jacques, the son of Nurse Cavell's great friend Madame Rappard, becomes a wanted man after shooting a sentry. He hides out in his mother's bar, but when a German platoon orders Madame Rappard to billet four of them, Nurse Cavell offers to hide Jacques at the Berkendael Institute. He is successfully smuggled out.

At the Institute, Nurse Cavell orders Jacques to change his clothes, and burns his uniform. He tells her there are hundreds more like him, forced to live like animals, and wishes that she could help them all. The Germans call, and Nurse Cavell hides Jacques in a small anteroom in the basement, concealed by a large wardrobe which the Germans fail to look behind.

Nurse Cavell contacts her friend Madame Pitou, the wife of a barge captain, and arranges to have Jacques smuggled to Britain hiding amongst barrels. Another friend, Madame Bodart, helps Jacques leave the Institute unobserved.

At the frontier, the barge is searched, but the barrels are not opened. A confident Madame Pitou asks the Germans to post a letter for her - it's a coded message to Nurse Cavell confirming that Jacques is safe.

As Nurse Cavell begins sheltering wanted soldiers in earnest, Baron von Bissing, the Belgian Governor-General, tells his new Military Governor, General von Sauberzweig, that he wants a crackdown on the number of escapees and refugees. Von Sauberzweig receives news that many escaped English prisoners are known to have rejoined the Allied forces.

Three soldiers pay Nurse Cavell a visit, but a well-rehearsed alarm system ensures the prisoners remain undiscovered (despite one of them nearly betraying his position with a sneeze). Madame Bodart, her young son Philippe and the Pitous assist in smuggling them out of the country.

An English aviator is on the run in Brussels, and sheltering him is deemed a capital offence. He successfully reaches Madame Rappart, who passes him onto Nurse Cavell's basement.

An escapee is recaptured trying to cross the frontier, and under interrogation he tells the Germans about Nurse Cavell's involvement - and that she's currently sheltering the English aviator. A platoon of Germans pays the Institute a visit, and this time they check behind the wardrobe - but the aviator has escaped just in time. However the German officer discovers an incriminating piece of paper and has Nurse Cavell arrested.

Before the trial, the US consul Brand Whitlock tries to get permission to defend Nurse Cavell, but his request is brushed aside. On 9 October 1915 Nurse Cavell, Madame Bodart and Madame Pitou go on trial. Despite the defence's plea that Nurse Cavell was only acting on impulses dictated by her profession, she is sentenced to death. Her co-defendants get fifteen years hard labour.

Von Sauberzweig orders that the sentence be carried out immediately. Whitlock's assistant Gibson warns him of what the execution will do to Germany's image, but is ignored. Gibson returns to Whitlock, who writes a letter to Von Bissing. Von Bissing receives Whitlock's letter, but explains that he can do nothing.

The prison chaplain informs Nurse Cavell that she is to be shot the following dawn. She asks to see an English chaplain, and tells him that she has no fear of death, and bears no hatred or bitterness towards anyone.

A firing squad is assembled, though Private Rammler is reluctant to get involved.

October 12, 1915. The last rites are read, after which Nurse Cavell is led from her cell to the Tir National, on the outskirts of Brussels. She stands in front of the firing squad. They are ordered to take up their positions. Private Rammler refuses. The chaplain prays.

Nurse Edith Cavell is buried in a plain grave.