If you don't have Showtime, but still wanted to see what the new season has in store for Dexter, Showtime has released the 1st episode of season 6 online for free.
"The explosively popular DEXTER® is back with a vengeance for a sixth season of startling suspense and unexpected twists. It's been a year since last season's shocking and heartbreaking conclusion, and mild mannered criminologist-cum-grisly serial killer Dexter Morgan has come to terms with who he is. But his existence is shattered when he crosses paths with an enemy unlike any he's faced before. A delusional religious zealot with unflinching convictions, this new adversary soon draws Dexter into a dangerous game that could well end in disaster."
To achieve a TV-14 rating and prevent an age gate on the video, the episode has been slightly edited from the original. It will still give you a good idea of what to expect from the new season in case you were considering purchasing Showtime just to watch Dexter.