Many viruses carry their genetic information in the form of RNA, and with the exception of the retroviruses replicate entirely through RNA intermediates. One such virus is lymphocytic choriomeningitis virus, which has now been caught red-handed in the act of illicit synthesis of DNA — seemingly through the agency of the reverse transcriptase enzyme used by retroviruses to produce DNA from an RNA template. The authors have taken great pains to rule out the possibility that this result is a false-positive artefact of the polymerase chain reaction, leaving a tantalizing puzzle that remains to be solved.