I agree, Pentas lanceolata.
They are often grown "as annuals" in much of the USA but they are actually perennials and will act that way in warmer winter zones. If you do prune it back to make a bushier plant, you can root the nice looking parts to have more plants.
The butterflies usually love them and the hummingbirds will even use some of the more nectar rich varieties. Plus, they'll bloom all summer!
Based on the nice rounded flower cluster, it also looks like it could be one of the tall, old-fashioned varieties that are becoming rare in these days of short and stumpy plant breeding. Hold on to it! The butterflies usually like the old-fashioned Pentas the best and butterfly gardeners are often trying to find these, usually in vain.
Here is a similar-looking, medium height cultivar:
there nice!
They are really pretty. And interesting to know they may be an old-fashioned variety. 
