Clark tensed up, he couldn't believe the words you had just told him, yet he could see you were telling the truth. You came to his apartment in Metropolis in the middle of the night, pleading with him to help you and give you an alibi.
When he asked you why, all you said was 'I murdered a murderer...' He stood there listening to what you had to say about the matter, how the man you murdered was the husband of your missing best friend. You told him how the last time you saw your best friend, she said that she knew her husband was cheating on her, and planned to confront him with the evidence, of the lipstick that wasn't hers on all his clothes, and the jewelry he bought with his joint account that was given to someone else. Then a week later, your best friend was declared missing, and when you went over to her house, the best friend's husband had brand-new tires on his truck, and he moved his mistress into their house. It was all damning evidence, but the police did nothing about it. So you took it upon yourself to get justice.
His first instinct was to fly your arse to the police station and dump you there, let the police throw you in prison for the rest of your life. But something was holding him back from that, you came to him of all people for help. You are his friend, and he couldn't just abandon you after you did that.
"Fine..." He sighed softly and pulled you into his apartment. "You were here, the entire time, alright?" He said softly. "We were here, watching movies... at least the apartment complex's security cameras are down.. so the police can't disprove it.."