Margaret withdraws all her cash by means of falsifying a cheque and buys clothes and a passport for Selina who convinced her she would escape from the jail; they were in love and the plan was they would both flee to Italy.
Selina was to come to her that night. Margaret sat up all night, waiting, and was heartbroken when she didn't turn up. Margaret went to the prison where she learned that Selina had indeed escaped. She rushed home expecting Selina to be there, but instead found the prison warder (the one who was in The Bill) at her door.
It transpired the warder had smuggled Selina out of prison, believing Selina loved her. Instead she had run off with Margaret's maid, who was Selina's maid before she went to prison. It was this maid who was smuggling the flowers and the hair into Margaret's bedroom, and feeding information to Selina.
The maid was also Peter Quick, in a wig and fake moustache. Selina and the maid were corrupting young, wealthy women and taking money from them.
The end showed Margaret committing suicide by jumping off a bridge into the river. At the same time, we see Selina and the maid on a boat, presumably in Italy. Selina senses Margaret's death and dives in the water.
The closing shots show Margaret and Selina embracing underwater.