This goundcover is growing in medium, moist shade. It began blooming in late July. Look familiar to anyone? I'm pretty sure it is not vinca. My current guess is ruellia.
I'd say that is a good guess. Not that I ever even heard of ruellia, lol, but I just googled it and the photo looks very similar to yours. Pretty little plant! Is it aggressive or behaved?
Almost certainly some form of plumbago, aka leadwort, aka Ceratostigma plumbaginoides. The spikey centers to the clusters of flowerlets are a dead giveaway.
Here is a link that might be useful: Hardy plumbago, from Dave's Garden