Creator: Robert Cochran, Joel Surnow
2001
This was the quartet of episodes when things cycled back around. Jack was reunited with his family; Jack returns to the office after several hours on the run; Palmer finally confronts Jack; the plot and its motivation is finally explained to us. And almost immediately things began to fall apart. Possibly this structure will be mirrored in the end--we'll have to wait an see.
Another note: it's really hard to do research into 24 without running into massive spoilers on the web. There's been a few times I've nearly learned some shocking truth about the ending, only to turn (or click) away in time. Yes, I know it's not going to end well (and it's going to be a cliffhanger, but of course). Yes, I know there's more twists to come--and more death.