There is not much happening in this chapter and did not expect that as well. After such a tense build up and release, Gosho likes to give a light hearted file. And this case also shall be no different. There will be a silly motive that's for sure.
Somethings that are worth looking out for:
-How Heiji will get out of the mess without revealing himself? Would he play along with that voice? That's too risky.
-if Heiji is found out, how will he hide the fact about voice changer? Will this evoke Ran's suspicion?
-How much Conan is going to fill Heiji in on Rum?