Pions??????

Which episode number is the one where Theresa was giving birth while stuck in a cabin with Ethan and Gwen; she had a hallucination in which the three of them did a dance together and sang the show's theme? If you can give me the exact date it aired, that would be great. Also, where can I watch that one episode? Can you give me a link? Don't say NBC, because they only have the latest episodes. Thank you!!!