I'm currently writing a period novel, in which the character is narrating the story some time after. I have reached a point in the story where another perspective is needed to complete the plot and keep it moving. In your opinion, which is the most clear and concise way to deal with this problem?
If you're telling the story as a retrospective, then you really should stick to your first person past tense narrative. If you need other POVs, you should use a straight third person narrative style, which permits more flexibility with multiple POVs.
We'd be able to give better advice if you were a little more specific as to why you need to change tenses/POVs...
ditto that... why do you think a change is necessary?... if it is, then you probably should have started in third to begin with and should consider changing it out of first...
Well, the story has some elements of a mystery, and one of the important occurences needed in order to make it complete is a rather hushed up one. There is absolutely no way the narrator would have been able to witness or hear of it. On the other hand, the story is very reliant on the emotions and perspive of the narrator, so I'm in somehat of a rut.
Is there a way for you to inform the reader through the main character without him fully realizing the meaning of the events that have taken place??
If you need to reveal disparate elements that fit together to reveal the puzzle, but must keep the narrator from piecing it together, you eiter need to make the narrator dumb as a sack of hammers, or tell the story from several distinct points of view instead of a single narrator. Otherwise, you must have a complex set of clues that only the main character is able to make sense of (the classic whodunit).
Look at Wilkie Collins' The Moonstone. A different narrator for each section of the mystery novel, which allows the author to manage the release of information that only some characters would have.