PLURIPOTENT stem cells are the source of an animal’s tissues. They have become a hot topic in medicine. Researchers hope to use them to test drugs, to make models of diseases, to grow transplantable organs and, one day perhaps, even to let patients regenerate missing or damaged parts of their own bodies.

Great promise, though, often brings great hype—and even scandal. The low point came in 2006 when Hwang Woo-suk, a prominent South Korean researcher, was charged with fraud and violations of ethics laws after the revelation that he had faked much of his apparently pioneering work in the field.

Now a different set of research is under the spotlight. On January 30th Nature published two papers by a team led by Haruko Obokata of the RIKEN Centre for Developmental Biology in Japan. In them, she claimed that she and her colleagues had found a simple way to reprogram ordinary mouse cells, persuading them to transform themselves into pluripotent cells.

Making pluripotent cells by reprogramming ordinary cells avoids the need to harvest them from embryos, their natural habitat, which is an ethically delicate matter. The first researchers to work out how to do it, in 2006, used genes for proteins called transcription factors, which switch other genes on and off, to make cultured skin cells pluripotent. This process (for which they received the 2012 Nobel prize in medicine) is, however, finicky. Dr Obokata’s papers suggested there was no need to bother with transcription factors. Instead, simply shocking ordinary cells—by pressure or a short bath in a mild acid—was enough to do the job.

It did not take long for doubts to emerge. The internet has accelerated the process of peer review, by which researchers try to poke holes in each other’s findings. Blogs and websites picked up on apparent irregularities in images and diagrams in the papers. One picture appears to have been copied inappropriately from Dr Obokata’s doctoral thesis. And a chunk of one of the papers seems to have been copied verbatim from elsewhere. Researchers around the world, intrigued by the possibilities offered by the new technique, tried to replicate it. The Knoepfler Lab Stem Cell Blog, a site that is keeping track of these efforts, reports nine failures and two pieces of encouraging news that nevertheless fall short of full replication.

The most definitive piece of bad news arrived on March 13th, when Kenneth Ka Ho Lee, a researcher at the Chinese University of Hong Kong, posted the results of his attempts at replication to ResearchGate, a social network for scientists that aims, among other things, to shake up the process of peer review. Having repeated the experiment three times, he found he could not replicate Dr Obokata’s results.

The day after, RIKEN held a press conference. The institute has formed a committee to investigate the claims. So far, it has decided that some cases of image manipulation were innocent mistakes, but is still investigating the rest of the worries—and RIKEN’s boss, Ryoji Noyori, has described Dr Obokata’s work as “sloppy and irresponsible” while Masatoshi Takeichi, the director of the developmental-biology centre, has suggested the papers be retracted. One of the authors, Teruhiko Wakayama, agrees. Another, Charles Vacanti, of Harvard, is sticking to his guns for the moment.

This may look ugly, but it is the way science is supposed to work. The point of peer review is to catch errors, to stop them polluting the record with unreliable knowledge. It may look unseemly to wash dirty linen in public. But that way everyone can check whether it has been properly cleaned.