Dear Pandora, it's not a fact that Stalker was the one who attempted to harm Ara; the role of the attacker is unknown. And he couldn't have been the destroyer, as Ar opposed Hermit at one time. And the fact that he called for a checker is not indicative. Such an experienced player could easily bluff the checker. Hoping that he would fall for it and not go to him.
Proof of this are the last two nights. Namely, the style of the attacks and their result ("the killer got lost in the crowd," "the killer entered through the back door"). The first time, the defense worked :) The clue was planted by the killer. The second time, it didn't work. But the murder is considered unsuccessful because the victim was healed. There are no clues. And none were planted.
Have I explained it well enough?