Mars Conjunct Pluto...

starts on December 13 (using a 1 degree orb), is exact on December 14 at 3.10pm in Kilmore, leaves on December 16.  Both at 4 degrees and 41 minutes of Capricorn.

Mars and  Pluto joining forces is a bit like leaving a pressure cooker alone unattended for too long... you must keep an eye on it and allow some pressure to release so it doesn't explode!

Both planets are pretty 'energetic' but in different ways... Mars tends to be 'in your face', while Pluto is more subtle, but deeply powerful.  The combination of the two suggests a powerful new start (conjunction) somewhere in your life - most likely as represented by the house position of this meeting of Mars/Pluto.  Obviously, the more conscious and understanding you can be with this energy, the more you will get out of it.
You may also want to look at which houses are ruled by these planets (ones with Aries or Scorpio on the cusp) in order to get a feel for what or who holds the chance for a powerful new start.

If you have personal planets and/or points in Capricorn, this is an especially powerful time for you.