An opportunity came for Elijah in the form of an invitation. Although it came late minute, it was a party held at Marcel's place but he would be dammed not to attend. He was not going to rescue Arianna, however, he needed to see the man that Arianna had chosen over him - and there was a part of him that wanted to see her as well even though he was full of anger, regret, and resentment.
Was she happy with Marcel? He hoped not, that was the only way he would feel peaceful - that she made a horrible choice. Elijah hoped that coming there would reveal everything to him and he would come to discover that it was all a misunderstanding.
That Arianna had no choice but to love Marcel because he threatening her. He prayed that her heart was still with him and everything else was a mere pretense. She was merely pretending to love Marcel to save her head, he hoped for that.