In the course of serving on a committee for a graduate oral presentation, I noticed something very strange looking in a Phys Rev Letter from a few years ago. While unlikely to be seen in a casual glance at the printed version of the journal, it was very striking when the figures were blown up to 4' on a side by a digital projector. Basically, it looks like someone used what I shall delicately term the "Photoshop operator" to massage their data. This paper has been cited 65 times since its publication, and has been milked heavily by its authors.
So, what is the right course of action? I've got no actual proof of fraud, just a very suspicious figure. I've now emailed the editors at PRL twice about this, and received no response from any human being - just the form letter generated by their mail system. Since this is circumstantial, I'm certainly not going to accuse anyone publicly. Next I'm going to call PRL on the phone. Updates as events warrant.