Rather late to this one - and the new Listener has just arrived. I do not understand how to complete the four quadrants. For the NW quadrant I have what I would term a "word ladder" with each answer (all across) being a one-letter change from the previous answer. The NE quadrant is all across answers being the same as the set of down ones. The SW quadrant appears to be (almost) normal apart from rows 2&5. The SE quadrant eludes me although it should be the one with down answers reversed.
It does not help that I cannot get three answers:
Course follows trail ending abruptly (swallowed by this?)
Extremely admired in animal communication field
Generally more accessible first episode?
Finally, what is the thematic element appearing in the same place in each quadrant?
All hints, nudges and help greatly appreciated.