Meg's medical saga was a bit far-fetched from the beginning. First, she (and her unborn child) survived a bus explosion. Then, she (and her unborn baby) survived the same bus plunging over a cliff and falling a very, very long way.
You may recall that everyone else on the bus died. But not Meg--she not only survived, but managed not to miscarry. Eventually, she even woke up from her coma. And then...boom. Dead.
Keith told Veronica that a blood clot broke loose. But remember how just after she woke up, Meg pleaded with Veronica not to let her parents keep the baby if "anything happened" to her? And remember how Meg had survived the explosion, bus crash and months in a coma apparently without a hitch?
When Duncan and Veronica left the hospital room after talking briefly with Meg, I had what I can only describe as a Lemony Snicket moment. You know, the reaction you have when someone says, "I'll tell you when I see you," and you know beyond a shadow of a doubt that the speaker isn't going to live to see that next meeting? And, just as I expected, we never saw Meg again.
(Plus, remember how they keep Meg's little sister in the closet?)
We were suspicious, but we figured a blood clot wouldn't be easy to fake. And then, long after we'd watched the series for the