The quality of the show, not the show itself.
Up until last night, I was having serious doubts about LOST's vitality for the rest of this season and beyond. The time jumping, flashes, time travel, whatever you want to call them, were a contrived plot device and lazy writing: the characters were miraculously saved from deadly situations, or just as annoying, right before a vital piece of information was disseminated to them, the sky would flash and they'd be pulled into another time.
Because of that, the on-island characters seemed to be going through the motions, thrown into random predicament after random predicament. Because the time jumping happened so often and so "randomly" enough, not much suspense was ever built up on the island, and LOST was starting to play out like a bad action movie, with its plot built around set pieces that didn't necessarily relate in any meaningful way. Add to that some redundant character development, like reminding the audience that yes, Sawyer really misses Kate, and the on-island plotline was becoming downright boring.
With regard to the off-island characters, the plot threads were so scattered that the show seemed to lack any direction whatsoever. I guess that happens when you've got a principal cast of nearly twenty characters, and they're not all in the same place geographically speaking anymore.
But the show came back in a huge way last night. I won't spoil it for you if you haven't seen it yet, but I will say a few things. If I may be so bold, I felt like I was watching Season One again. There were some great dramatic reversals. A few off-island threads came together (thank god). Some new mysteries were introduced, but they didn't overshadow the narrative drive of this season--that of getting back to the island. And yes, finally, the time jumping became less of a plot convenience and caused major problems. Last night's episode gave us plenty of action, plenty of oh-wow moments, and did plenty to push the story forward after it had been slogging along for four or five episodes.
1 week ago