Ben Jackson is an Able Seaman in the Royal Navy in 1966 who finds his way to a night club called Inferno. He is a bit depressed because he is assigned to a six month shore leave while his ship is deployed to the West Indies. Polly and Dodo, who are also at the club, take it upon themselves to cheer the poor fellow up.
When Polly gets hit on by an insistent jerk, merchant marine, Ben steps in to defend her. One thing leads to another, and the pair of newcomers are caught up in helping the Doctor with his struggle against WOTAN and The War Machines.
By the end of the adventure, Dodo has decided to stay on earth, or at least that's what Polly and Ben tell the Doctor as they try to return her TARDIS key and inadvertantly get carried away in the time machine.
Along the way on their adventures, Ben and Polly become quite close, and Polly doesn't seem to mind Ben's protective nature toward her. Ben finds her to be rather elegant and Posh, and gives her the nickname "Duchess".
Ben and Polly are both there when the Doctor regenerates for the first time, and they continue on traveling for a time with this new incarnation. All good things come to an end, however, and when the TARDIS finds her way back to 1966 London, the couple decide to stay behind. The Doctor presumes that the pair will remain happily together for quite sometime, and apparently that is the case as we learn later from Sarah Jane Smith, that Polly is now working at an orphanage in India with Polly.