Surprises in stories are about enjoyment. In order to really enjoy a satifsfying surprise I need to be expecting it in some way or another – although I should certainly not ‘see it coming a mile away’. The surprise has to be in some way meaningful – therefore it has to be in some way expected. An unexpected surprise is not meaningful, it just interrupts my enjoyment of the story.
Enjoyable surprise: “Ah! The butler did it! Of course: we learned earlier that he was in love with the gardener, and had acces to poison. But I never expected that nice man…. of course I did, that’s the whole point. You never know what lies hidden in the human heart. And yet you do…”
Unenjoyable surprise: “Ah! The butler did it! But why? I have no idea.”