is this the one (spoiler!) ?
... whith the picture taken of the murdered people in front of a boat. and they way the people are standing in front of the boat reveals the riddle.
I think the solution was, that they needed to arrange the way of murders with the letters of the boats name. sorry for my bad english.
looking for this particular picture with this ending for some time. I am not so sure, if this movie could be the one. thanks for your help.
br, daniel