Act One

Captain Henry Cadogan sits in a trench in the Somme in 1918. He is reading a letter from Nurse Irwin. She writes about how she misses him and how she often thinks of him. She reminisces of times, four years past, when they were together, writing of picnics and swims, and wonders what ever happened to Spratt, a young man whom they taught to swim and who once rescued Henry. She remembers how brave he was and wonders if he is still as brave, now that he is a soldier. Just then, Spratt runs in and delivers a note to Henry. He is stationed with him. Henry tells him that he thinks it is almost time to go – there are explosions all around, and they are getting closer... and worse. Henry finishes the letter and gives the sign that it is time to move. Spratt panics for a moment, but then Henry urges him onward.

It is 1914 on the shores of Lake Windermere. The boys of St. Michael's are in the midst of a dry-land swimming class. The instructor assures them that, by learning all of the techniques on land, they will be far better swimmers than those who just struggle to learn in the water. He tells them how swimming and singing are similar, in that they both are good for the lungs and the soul. He makes them sing the motto to show that music and muscle can go hand in hand ("Swim for Victory"). As they sing and practice, the girls from St. Catherine's come by, for they are in the middle of a leisurely day of picnicking and picking flowers. The boys' instructor tells them that they will have three new boys joining them.

A train has just pulled into Oxenholme Station and Agnes, age 12, Dick, age 15, and Jack, age 11, step off. The three Spratt siblings seem a bit lost and have notes pinned to them that say, "To be delivered to the Warden of St. Michael's, Kendal." Next, Maggie and Geordie Irwin rush in, having just arrived, as well. The Porter gathers the boys and girls together and readies to send them on their own ways. The siblings that are being separated all must say goodbye and wonder what life will be like now ("Oxenholme Station").

The boys are on their way to St. Michael's. Joss, the post boy, and Dick are getting acquainted. Dick explains that he has been sent here because he is a pickpocket and he can't help himself. Meanwhile, Jack is talking to Curly, who is one of the school monitors. He has brightened up quite a bit from the sullen state that he was in at the station. Dick explains that he has never been out of London before, so if you show him wide-open spaces and frogs and sheep, he gets quite excited ("Never Been Away from London"). Mr. Kingsley takes a moment on the way to explain to the boys what St. Michael's is, for they have been told nothing. It is a home for boys where they live and relax and eat and learn. The home is best known for its swimming prowess. At the mention of swimming, Jack begins to panic – he is afraid of water.

The girls have arrived at St. Catherine's. They are greeted by all of the girls from the home, as well as Lady Cadogan, who is the home's chief patroness, and her children, Olivia and Henry. The girls then sing a welcome song to the new arrivals ("Welcome to St. Catharine's"). Agnes suddenly realizes that she has her brother, Jack's, medication and she speaks up, asking what to do. The staff women ignore her. This angers Maggie, and she yells at them for not dealing with the problem. Henry stays behind for a moment to applaud Maggie's outburst. Then, Miss Appleyard confronts Maggie. Maggie does not apologize or show remorse; she continues to stand up for herself. Miss Appleyard is pleased, in a way, at how honest Maggie is and that she questions things. This is new for the home, for most girls just go along with things as they are. The two form a bit of an alliance with one another. A bunch of the girls come back out, wondering what sort of punishment Maggie has gotten. She explains that she likes Miss Appleyard, and that they want to make the world a better place. The other girls don't understand: most cannot read or write and never have thought or dreamt. Maggie tries to encourage them ("Get out There!").

Back at St. Michael's, the boys have just finished evening prayers when the staff has an announcement. Two more boys have passed their swimming proficiency exam, and another boy has received a bronze medallion. No boy in the past six years has left the home without being able to swim. It is now wash time, and the boys are all assembled with prepared bowls of water. The boys sing about water being everywhere – for washing, for drinking, for swimming ("Water Water"). Jack is pretty afraid of the whole scene.

The Cadogan family is sitting around. It has been a week since the new children have come. A post comes from the War Office. Lord Cadogan must go to London to see the War Minister. The situation seems bad – they want more munitions and gunpowder. The heads of the two schools arrive to give a briefing on the new children. The first exhibition swim of the year is coming up, and Henry is asked to lead the boys in a swim across Lake Windermere.

The girls have all gotten together, and it is obvious that Maggie has become quite popular. She is the confidant of many of the girls. Just then, the boys arrive for country dancing. Agnes reunites with Jack for the first time and finds out how terrified he is that they are trying to teach him to swim. She tries to encourage him, when Miss Marchant, the head mistress, scolds them for not dancing and makes a remark about Jack not swimming. Agnes lashes out and sticks up for her brother. She is led away by Miss Marchant, and Maggie approaches Jack as Henry watches from a distance. Maggie convinces Jack to let her teach him to swim. They will meet every morning before breakfast and be back by roll call. Henry hears the plan and approaches, asking if he might join in. Jack runs off to go dance, and Maggie and Henry are left alone for a moment. They catch up, then Henry rushes off to go practice swimming; he has never swam across the lake before. Maggie spends a moment alone, reflecting on the help that she is giving and the changes that she has been making ("Whichever Way We Go").

Dick, Joss and a few other troublemakers have gathered to trade cigarettes and to come up with some new schemes to make money. Meanwhile, the boys are gathered by the lake for their final swim lesson before the exhibition.

Act Two

The boys have all been assembled, and Lord Cadogan addresses them. He explains about the war that has broken out in Europe and that, as of midnight that night, August 4, England has declared war on Germany. The girls are assembled, as well, and being spoken to about the same subject. They are being told that all efforts will now be wartime efforts and that they must do their part to support the men who are fighting and the people who lose loved ones in war. They are supposed to have a sock-knitting class every night now. This puts Maggie over the edge, and she shouts out and insists that they must really support the war by learning to be nurses and truly help the troops. All the girls jump up and applaud and support her while the staff women have a heated argument about what to do.

Activities will be changed for the boys, too – there will be serious cutbacks and they will be training for war. The one thing that is agreed upon is that the swimming exhibition will still happen and the money it raises will go to the war efforts.

Miss Marchant is arguing with Miss Appleyard in her office. She feels that, not only is Miss Appleyard encouraging Maggie and the other girls, but enabling them. Maggie is called in and told that she must apologize. She is defiant, but Miss Appleyard assures her that, "to win a big war, you must lose a few small battles." Angry and humiliated, Maggie apologizes.

Some boys, including Henry, are trying to get through to Jack. With all of the talk of the swimming, he is terrified again. Finally, he lets loose and explains the origin of his fear. Back at home, his siblings were never around, and he was often alone with his mother. She did not like him and used to lock him in a cupboard. Even worse, she used to hold his head under water until he couldn't breathe. Many of the children wonder to themselves what it is like to have a mother who truly loves you ("What's it Like to 'Ave a Mother").

The troublemakers have gathered again and have a plan in motion. They will get treacle toffee from the mines near the home and send it to Dick's friends in London for a profit. They are not worried about the war; they plan to become rich with their scheme.

Meanwhile, Maggie and Henry are at the lake with Jack for his swimming lesson. He hesitates at first, but, once he is in and going, they are amazed at what a natural he is. He seems to have conquered his fear and is even a very good swimmer. Geordie is there, too, and they all tease Henry about not having swam across the lake before. Jack jokes that he will swim with him and will hold his hand when he does the swim at the exhibition.

The boys have arrived with the Maypole to set up for the next day's festivities. Geordie is looking for Jack, and Maggie whispers to him that he is out, swimming with Henry. He swam a mile and a half the day before. There are claps of thunder – a storm seems to be moving in. They are worried about being able to swim; by the lake, there tend to be electrical storms with lots of lightning. Finally, the three boys who will join Henry on the swim are announced.

The troublemakers are convened at the train station. They are going to ride up to the mine, stock up and bring back the loot to send out on the next train. Hannah, one of the girls involved, runs in and tells Joss that she just found out that the mine is not a treacle mine but is filled with gunpowder. There is an electrical storm going on, and the boys are probably smoking. They are in great danger, being in a mine that is filled with gunpowder. The two rush off to catch the other boys.

Alarms are going off at St. Michael's, and all of the boys are gathered for a roll call. There has been a huge explosion at the mine, and two bodies were found. They find out that Dick and Midgeley, his partner in crime, are missing. Joss and Hannah have been brought in, and Hannah, in a panic, tells everything and blames it on Joss.

The staff are gathered that next morning in the office. They cannot believe the night that just occurred. One boy is dead and one is critical. The children send a representative to tell the staff that, despite what has happened, they wish for the day's activities to continue. The staff agrees that they, too, would like to see this happen. The Spratt children, along with Maggie, come in and are informed that their brother has been killed. Jack explains that Midgeley was supposed to have been swimming and that he wishes, as a tribute to his brother, to swim in his place. All gather at the lake, and the festivities carry on as planned. There are great performances and much rejoicing, as well as a few somber moments to remember the boys who were in the accident. Then, the swimmers take their place. Henry and the other two boys dive in, leaving Jack trembling on the side. He summons the courage and dives in.

Maggie is sitting in her hospital tent back in 1918, in the thick of the war. She is writing a letter to Henry about how she is where she wanted to be, but they are all tired of war. She imagines that she is very near him and just hopes that this will be over soon. Just then, Henry, led by Spratt, pushes through the warfare and arrives at the hospital tent. Spratt lies Henry down; he has shrapnel in his leg. At first, none of them recognizes each other, and then they slowly realize: the three are reunited again.