This summer, four young women set off on vacations in Southeast Asia. Here's what they had in common: They were all from North America; they were all in their 20s; they were all pretty, bright, adventurous. And one more commonality: They all died.

Two of these deaths occurred in June in Thailand, two in June in Vietnam. All four women were diagnosed with the symptoms of acute poisoning. And while some explanations have been offered by the authorities, these have been either vague, improbable (see my recent post on the deaths in Thailand) or opaque (see CNN's Friday story on the deaths in Vietnam). My favorite statement is one from the Thai police declaring that it could be "months before official results are revealed if ever." (Emphasis mine).

If ever? What kind of a police response is that? Does it mean that investigators know something they don't want to tell? Or that they don't have a clue? It's no wonder that the rumor mills are spinning stories of murder, of a serial killer stalking female tourists in Southeast Asia, of a police cover-up to protect the valued tourist industry. The serial killer idea, of course, builds on earlier mysteries: the 2009 death of a Seattle woman, still unsolved today. The similar and also unexplained death of a 22-year-old woman from Norway the same year. An odd cluster of deaths in another Thai city during winter of last year, including a 23-year-old woman from New Zealand.

The other theory circulating is that the police are covering up the careless use of insecticides by Asian hotels; an explanation denied, of course, by the hotel industry. It doesn't explain, of course, why most of these deaths involve females in their 20s. But there's some support for it from an independent investigation into the 2011 death of New Zealander Sarah Carter.

Read the rest of the story at Wired.com.