Potential killers/motives:
Kate: She’s angry with his return and that she did the deed with him and he could be threatening to reveal it to Stefano.
Stefano: He knows Kate and Ian were together and he’s going to get his revenge by setting it up to appear as though Kate killed Ian and then he’ll pretend to ‘save’ her from being arrested and sent to jail.
Brady: He wants to be with Madison and she is being threatened by Ian.
Madison: She wants to be with Brady and Ian is stopping her.
Victor: He wants to be rid of Ian as head of his company and hates that Brady can’t be with the woman he loves.
ISA: Ian is the guy that they are trying to nail for something evil.
EJ: Ian is blackmailing him over something to come out in the future – maybe Ian is his real father??? lol
Anyone I missed in the potential killers? Remember this is all speculation not spoiler.