A famous violinist enlists in a music school in order to woo one of the students.
In 1914, during the First World War, the rich chatelaine de Boissière, with a sulphurous past, took in Jean le Barois, a young soldier lost in territory occupied by the Germans, who was none other than the son of the man she loved, then ruined. The young man, after having despised her, falls madly in love with the woman who pushed his father to suicide.
In 1885, La Guillaumette and Croquebol are two cavalrymen who are constantly victimised by their superior, adjutant Flick. One day, the two men are given an opportunity to redeem themselves by recovering four horses that have gone astray. Unfortunately, they follow the horses' example by taking the wrong train. When they finally make it back to barracks, after a long series of mishaps, they are rewarded with sixty days in prison.
A woman's marriage is on the rocks ; to avenge herself, she decides to take a lover for one night .So she buys all his stock from a balloon man and flies them through the Parisian sky ; all her balloons carry a message :"I will be alone after midnight" (hence the title); a lot a suitors comme to the rendezvous : a fisherman, a soldier, a traveler , a gentleman cambrioleur (a nod to Arsène Lupin?) and others ,much to Michel, a young man in love with her's displeasure.