Barge girl Kay enjoys a rugged existence with her adoptive father "Skipper" and his son Steve transporting goods on their boat along the canals and rivers of England. Arriving in London with a barge full of bricks, Kay admits to her dream of becoming a film actress. Steve teases her about her ambitions. Practising a song and dance routine on deck, she is spotted by Anthony Gulliver, a millionaire who is fishing in the Thames. He sees Kay's star potential and introduces her to another of his protégés, the abstract artist Sylvester. Steve is jealous of Kay's new friends and assumes that Gulliver's intentions are less than honourable. He locks Kay in her room to prevent her meeting the entertainer Dickie Randall at Gulliver's house. However, she escapes by diving into the canal, then hitching a lift with a rag and bone man. Arriving at the Gulliver residence wet and dishevelled, Kay immediately arouses the displeasure of Victoria, Gulliver's spinster sister. Tired of her playboy brother's propensity for taking artists and performers under his wing, she threatens to move out and let him fend for himself.
Dickie Randall and his wife arrive and Kay is given the chance to audition for one of Dickie's shows. Overwhelmed by the situation, she gives a terrible performance. Dickie's wife is nasty to Kay and this provokes the sympathy of Gulliver's sister. She resolves to teach Kay to sing and dance and to make her into a lady. Steve realises that Kay has escaped from the boat and he comes to Gulliver's to find her. Dickie Randall's wife is very taken by the rough, tough Steve and they go out for the evening together. Later Kay and Dickie's wife fight over Steve - it is obvious that Kay is in love with the man she has known as a brother even though they are not related.
Gulliver takes Kay to a nightclub where she dances with Dickie and watches him perform a song and dance routine. Kay prepares a late supper at Gulliver's house and entertains her new friends with a pastiche of Dickie's earlier performance. It is here that her talents shine through and Dickie realises that she has star quality. He also admits that he is in love with Kay, but when he tells her this, she brushes it off.
Kay rows out to the barge in her nightclub finery to join the Skipper's birthday party. Among the rough and ready barge men she sings a beautiful song in tribute to the river Thames. When Steve arrives, they share a tender moment, before being interrupted by a publicity man taking their photograph. Steve announces that Gulliver is lending him some money to play the stock market and that he will leave the country once he has earned enough cash. Kay is upset by this and also by the fact that Steve is still seeing Dickie's wife.
Gulliver sponsors a show that will showcase the talents of Kay, Dickie and Sylvester. Meanwhile, Steve is doing well on the stock market and buys himself a schooner. Kay goes out to visit the boat and just as they are about to kiss, the publicity man takes their picture. Steve assumes that this is a publicity stunt Kay has arranged for her forthcoming show and is very angry. He resolves to begin his travels very soon. However, when attending the opening night of Kay's show "Barging Along" he finally acknowledges to himself that he loves Kay more than just as an adopted sister and Kay admits that she feels the same way about him.
