Polly first appears in the First Doctor serial, The War Machines, where she is working as a secretary to Professor Brett. Brett develops the artificial intelligence known as WOTAN, and Polly meets the Doctor and Dodo when they come to investigate it. Polly befriends Dodo and takes her to a London nightclub called the Inferno, where they meet Ben Jackson and try to cheer up the merchant seaman. When Polly is accosted by another patron in the Inferno, Ben comes to her rescue. Eventually, Ben and Polly aid the Doctor in his fight against WOTAN when the computer tries to take over the world. They are the bearers of the news of Dodo's decision to stay in 1966 to the Doctor, and accidentally get carried away in the TARDIS when they try to return Dodo's key to the time machine.
Polly, in contrast to Dodo, is a more sophisticated and hip young woman of the 1960s — vivacious, attractive, and alternately shy and aggressive. She and Ben make an odd couple, but she is receptive to Ben's protective urges, and he in turn finds her elegant and posh, giving her the nickname "Duchess". Polly is present with Ben when the First Doctor regenerates into the Second, and continues to travel with the Second Doctor.
Eventually, the TARDIS finds its way back to 1966 London on the very day Ben and Polly had left (although about a year had passed for them). They decide to remain behind to resume their lives without disruption as the Doctor and Jamie travel on.
What happens to Polly after her return to Earth is not known. The Doctor seems to think that Ben will become an Admiral and that Polly will look after Ben, but it is unclear if this is a prediction or simply wishing them well.