This week Material World looks into what happens when published research is wrong, or worse fraudulent? When a published peer reviewed article is subsequently found to have something wrong with it, journals may send out a "retraction notice". But do these notices tell the whole story? Research out this week suggests that up to two thirds of retracted papers are due to scientific misconduct, rather than simple error. Also ecologists ask the public to help them identify 2 million bat calls and test tube spiders; how one of the largest British spiders has been reared in captivity and is now being released into the wild.