"Indeed. As we now know, this led to the series of burglaries. I had only a dim and fragmentary understanding of these matters until a fortnight ago, when we found that document in the wall at Bedlam. Then all became clear. But, too, it was clear that the buyer’s search was doomed to failure, for Hooke’s receipt mentions a certain ingredient without offering any explanation of how to obtain it. For that reason, the document was useless as bait for the Stake-out."