"The Flower with the Deadly Sting" is one of those 'giallos' that leans more in the melodrama direction than 'horror' - which isn't a BAD thing, though I typically prefer my 'giallos' with a higher body count.
A respected surgeon is involved in a weird love triangle affair with two half-sisters. When one shows up at his pad, he gets a little miffed and - following a bit of a struggle - she falls into his house plant-shaped sculpture made of daggers. He ends up dismembering her and disposing of the remains, which leads to the sister expressing concern over the missing woman. There's a bit of a mystery as to whether anyone caught the doctor in the act and around the last ten minutes is when a killer briefly shows up...
Not an awful film by any stretch - but, again, I like these types of Italian 'giallo' murder mysteries a little more on the "rougher" side. I'll give "The Flower with the Deadly Sting" a definite 'pass' for the lesbian SCUBA-sex scene, however. That was nice...