Indagatrix is an old-fashioned term that refers to a female investigator, detective, or inquirer. If you're looking for synonyms for indagatrix, there are several options to choose from. One possibility would be sleuth, a term that conveys the idea of someone who is clever and persistent in their search for information. Another good option might be gumshoe, which has a similar meaning and is often associated with the hard-boiled detective genre. Other options include private eye, investigator, detective, and researcher, all of which capture the notion of someone engaged in a systematic and rigorous pursuit of the truth.