Mr. Owen could only come to the island in one way. It is perfectly clear. Mr. Owen is one of us.
These words from Wargrave in the middle of Chapter IX mark the second crucial turning point in the novel (the first occurs when the recorded voice accuses the guests of murder). Prior to this moment, everyone has assumed, at least publicly, that their homicidal host, Mr. Owen, is hiding somewhere on the island and planning to murder them. But after Lombard, Blore, and Armstrong conduct an exhaustive search of the island and find no one, Wargrave boldly states the only plausible conclusion: the killer is one of their party. He speaks aloud what many of the others have considered but kept to themselves. This realization fosters paranoia and suspicion that build as the novel goes on and everyone begins to suspect someone different. This quotation also marks the point at which Wargrave steps in as leader of the group, a role he occupies until his apparent death four chapters later.