I'd like to see some interaction in the shop between Emily and Hannelore. Given they are both highly intelligent and mathematically inclined, I can see them, one slow afternoon, proving Goldbach's conjecture* on the blackboard -- and then wiping it off and thinking no more about it.

(hey, it's my headcanon . . . )

* every even number is the sum of two primes. This has been shown for every even number up to 4,000,000,000,000,000,000 and everyone believes it is true but no-one has managed to prove it.