There is already a full-blown turf war raging between Mrs. Elton and Emma but another one appears being ready to erupt between Mr. Knightley and Mr. Churchill.

Nothing much escapes Mr. Knightley's penetrating radar as he turns it on Frank and Jane's peculiar behavior when in each other's company. From Ch 41 (and indeed most of the chapter Miss Austen plants this possibility firmly in the reader's head)

".....brought him yet stronger suspicion of there being a something of private liking, of private understanding even, between Frank Churchill and Jane...."

Could our noble Mr. Knightley be (gasp) jealous of young interloper Mr. Frank Churchill?

There's nothing quite like a new rooster (a young, handsome, and charming one at that) in the hen house to upset the status quo in Mr. Knightley's heretofore comfortable Highbury barnyard!