I just had a thought. Not accusing anyone, just thinking out loud here. LE reportedly does not want a poly from the dad. Dad's first night out of the home for a job. A sick child. Two little boys...
Bear with me - I'm getting there. I just got off the phone with my mom who is alone with our 2 kids this weekend. She said it wasn't going well and they wouldn't go to sleep. DD was crying for us. I finally told her to let them in bed with her to watch a movie and eventually fall asleep (my mother is too old to get worked up trying to get them to bed).
Then a light bulb clicked: what if (I'm just speculating) this is the mom's first night ever with baby Lisa and both boys? Baby Lisa is sick, the boys are active, maybe dad usually helps with bedtime routine. I know my own DH helps tremendously at bedtime in our family. So - what if there was an accident? It's only been recently - last couple of years, maybe? - that they had said don't give Benadryl, etc., to young children, especially to "get them to go to sleep", etc. What if mom finally had had enough and gave the baby something to get her to sleep?
I honestly am suspicious of her reactions - more so than dad's. He seems totally shell-shocked, puzzled, doesn't know which way is up, overwhelmed. Almost catatonic in some videos. I think he is honestly shocked and trying to figure it all out.
However, sometimes truth is stranger than fiction so who knows what really has happened to little Lisa? It could be a stranger, an acquaintance, a family member/friend, or the parents. I feel like a dog chasing its tail on this case.