In And Then There Were None why does Dr Armstrong disappear?

Answer 1

He wanted to create the most unsolvable, greatest, mystery death that nobody could solve. He had been a judge for so long and he wanted to do something bad. He had a craving to kill, so he decided to make this scheme and make a billiant death of 10 people tha would be hard to solve, until someone found his letter in the bottle...basically, he had a craving to kill and he wanted it to be a really big, unsolvable death, so he did it according to the poem of the ten little indian boys

Answer 2

He formed an alliance and faked Wargraves death so they could capture the criminal. Therefore he was the only one who knew Wargrave was alive. Wargrave then pushed Armstrong off a cliff telling him there was a cave and to look over the cliff to continue murdering without suspicion because no one besides Armstrong knew he was alive.

Answer 3

Dr. Armstrong disappears because he is being hunted by the killer, who is systematically eliminating the guests one by one. He becomes paranoid and attempts to evade the killer, leading him to isolate himself.

Answer 4

He went to the beach, because Mr Owen told him to. When the three left found out that Armstrong has disappeared, they think he's Mr Owen. This is causing confusion.