The moment that Watari spoke of still having the future to discuss options, his eyes grew wide, and his left hand clutched at his chest.
L stood by, watching helplessly as his best friend fell from his chair and landed limply on the floor. There was no need for him to ask whether it was mere coincidence or not, L knew that this was Kira's doing, and that he, himself, had no more than a minute left to live.
Just as Watari fell to the floor, the automatic doors to the room slid open, and L saw Light saunter casually in. Taking in the scene, his attention turned from Watari, lying motionless, and beyond saving next to the chess table, to L, who stared helplessly back at Light, like a lost child would when trying to find a parent.
Keeping quiet, L slowly walked over to stand beside his lost friend's body. The tears that he longed to cry, evaded him, and the only thing he could do was to shut Watari's eyes, which had frozen open in fear.
The clock was ticking, and every second that past seemed to L like a second wasted. But it was all over now.
"Light…." L felt a sharp pain in his chest and couldn't finish what he was saying; he slowly sank to his knees and fell onto his side. He wanted to scream in agony, but his voice was lost. All he could do was lie there in pain, and wait to die. And while his eyes could still see, he silently scanned the room, and when he'd found his target, he conveyed a wordless message. "Even if I'm gone, there will be others to take my place. I knew that it was you all along, Light Yagami…I just couldn't find the right evidence to prove it…."
The world around L began to fade, slowly blackening in at the edges, and slowly closing in. He tried to breathe, but couldn't gratify the ache in his lungs as they begged for air.
"Looks like it's all over L," Light sneered just as L's vision finally gave out, leaving him in darkness.
With the last few seconds of his life quickly draining away, L thought of those that he was leaving behind, and those who would maybe soon follow. He thought of the promise that he'd made to himself to apologize to Watari for not believing his judgment, "Watari, it looks like I've failed after all. I guess, this case was just too big for me to take. I'd like to say I'm sorry, for not believing you last night. Sleep really was all I needed…and maybe now, a little bit longer left to live...But see you on the other side my friend, at least, I got to leave this world with you…."
L's heart stopped beating, and went silent. The world's greatest detective had been defeated, by the cruelest of all criminals.