The group goes back to the house and discovers the boarded up attic has been broken into! When they go upstairs, they see that at least 20 years worth of dust has built up but has recently been disturbed, some small footprints can be made out. They seem to lead to a hydraulis, a piano-like instrument. There is water dumped onto the floor nearby.
When they solve the puzzle, a panel beside the instrument opens up and they find a tunnel with a ladder built into the rock wall. They descend down and hear the sound of flowing water.
They find themselves in a beautiful underground grotto, with the moon light shining down through cracks in the cieling to the centre of the cave where a massive old tree grows.