Film Theory: The Aliens In Signs Aren't What They Seem...

Of course, the most compelling piece of evidence that can be drawn from this theory is the demons’ one weakness - water. Water belonging to a priest, in a house that could have once been described as ‘of God’, rendering it the one and only exorcism favourite: Holy Water. Most importantly however, it’s water that has been drunk by the little daughter Bo, the representative angel among their forces that will defeat the hoards of evil.

It seems rather random for Graham to start regaling his children with the tales of their birth when they’re moments away from their death, but in the context of our religious interpretation, it’s the precise point where everything becomes clear.

Bo’s birth was a miraculous affair, in which a newborn baby impossibly smiled at her father, in which she was so beautiful she shocked the entirety of the ladies attending Colleen, and in which she is directly referred to as “an angel” by all those that witnessed her. Bo might be a little girl, but in being such, she’s the unstoppable force of good within the Hess family - and the key to defeating Graham’s demons in the process.

It’s Bo’s water that offers a reprieve from their attackers. What is seemingly a mild annoyance is actually a wider attack plan put in place by the quirky little girl, who even reveals as much from the easy-to-dismiss line of “there’s a monster outside my room. Can I have a glass of water?”

She’s directly asking for the resources to fight against the demons plaguing the Hess’s, the only one aware (whether subconsciously or not) of what it takes to defeat them. The simple act of Bo drinking the water transforms it from plain to blessed, taking on her angelic qualities with each glass drank from and left out. If that isn’t enough, Bo’s name itself is derived from an Old Norse nickname Bua, meaning ‘to live’.