Direct answer
Objectives follow journal display order. Some depend on your choices; follow the active objective in the game.
Result
While walking along the shore of the lake near Kaer Morhen, Geralt came across the body of a drowner. The witcher thought at first that Lambert or Eskel had killed the creature - but upon closer inspection he soon discovered there were no marks dealt by sword or Sign. It was thus clear someone - or something - else had done the drowner in. They say the enemy of one's enemy is a friend, but Geralt wanted to see who exactly this drowner-killing "friend" was.
