anchor: At six o'clock, Miss Howard, disguised as Alfred Inglethorp, enters the chemist's shop, with her story about a dog, obtains the strychnine, and writes the name of Alfred Inglethorp in John's handwriting, which she had previously studied carefully. 
positive: Miss Howard went into the chemist's shop in a disguise which made her look like Alfred Inglethorp.
negative: Miss Howard never made any attempt to impersonate Alfred Inglethorp.