Here's a completed version of the story with the appropriate articles:

Yesterday I was sitting on **the** six o'clock train when I saw **a** strange man walking along the platform. He came into the carriage of **the** train where I was sitting, and he sat in the seat opposite mine. He opened **a** newspaper and started reading it. On **the** front page of **the** newspaper, there was **a** picture of **a** bank robber. The words under **the** picture were: 'Wanted by the police'. It was **the** same man!