Tick, tick, tick...

According to Jordan Chase in one of the two clips posted below, that's the sound of Lumen's life slipping away.

Will Dexter save his new love's life in time? Or will she suffer the same fate as Rita? That's the main question viewers are asking themselves as this Showtime hit concludes season five on Sunday with "The Big One."

Check out a pair of sneak peeks from it now:

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.