a lot of your questions were answered. rebecca went into the water tank because she saw a strand of lilah's red hair next to it. the moment happened quick. you were talking about connor/oliver when it happened, so you might've missed it. as for why laurel held on to michaela's ring. she said why. michaela was a mess the night of sam's murder and she also saw how close michaela was to going to the cops and confessing. so laurel held on to the ring knowing that as long as the ring was missing...michaela would keep quiet for fear of it being found and her getting caught. i remember the first time i saw that reveal my jaw was on the floor. the plot-point is there to show how conniving and vindictive laurel can be even though she's the "quiet one" in the group. ending the season with rebecca's death was a great cliffhanger. it leads us into season 2, but that doesn't necessarily mean it's the only mystery in season 2. hope you keep watching this show. season 2 is also really great!