Well, they now have Kay Panabaker (almost 16.5 year old) playing Lindsay, when the original Lindsay is now about 13 year old.

as for other cases that went past multiple episodes, there was also the "blue paint killer". that one spanned 2 or 3 seasons, i believe. it wasn't 3 episodes in a row, but they all dealt with the same killer.

i'm glad this didn't go for too many episodes, but i feel like the kidnapping was resolved much too easily. "hey, the chairs match!"