I must confess that I love SEAL Steve, so this is a great spoiler.
Here is what Peter Lenkov told TV Guide:
Executive producer Peter Lenkov tells us that there will be a McGarrett flashback late in the season that is actually a direct prequel to the pilot.
“The flashbacks take place hours before the pilot began in Korea,” Lenkov says. “You’ll get to see McGarrett in training as a Navy SEAL. The idea is that McGarrett had actually gone into North Korea with another Navy SEAL, a man who saved his life and was killed there.” So will we see familiar faces as well? “We’re hoping to bring back one of the Hesse brothers,” Lenkov says. “We’ll see what actually happened with Hesse in Korea.”
I think it can’t get much better than this. Am I biased? Hell yes! After all, Steve is my favorite character and in my eyes the most interesting one.