CONTEXT

13.10.2009, Tue Los Varanos recieves the Death Note by trading Sayu for it. 99% of the SPK dies. Mello makes a plan to interrogate Beyond.

14.10.2009, Wed Mello starts testing the rules of the Death Note.

15.10.2009, Thu US gang members die.

18.10.2009, Sun Sidoh shows up at Los Varanos. Kal makes the eye trade.

26.10.2009, Mon Kal and Mello interrogate Beyond at the State Hospital Beyond is placed in**.**

As soon as Mello skims over the rules for the first time, he freezes on the one about the Eyes. Internally he goes “BEYOND HAD THE EYES — BEYOND HAD A DEATH NOTE BACK AT WAMMY’S — THERE’S MORE THAN ONE DEATH NOTE.” He immediately puts Matt on the task of finding out where Beyond is being held.

They know Beyond’s real name from the news back then, and Matt quickly figures out through a few phone calls that Beyond is confined in a place similar to the Atascadero State Hospital.

Mello starts making plans to question Beyond under some pretext, hoping Beyond might have information about the Death Note that neither Near, nor Kira, nor L ever had access to, and maybe even to convince him to cooperate.

Being in LA, close to Hollywood, I’m 100% sure the gang has contacts to some highly competent makeup artists to create a face mask for Mello. They use Kal as a test subject to ensure the mask is good enough to hide his name and lifespan. Mello and Kal both go to the prison, taking Sidoh with them and a prepared page from the Death Note to look like a Rorschach test or something idk, some kind of paper, Beyond has to touch. Maybe they pose as psychologists wanting to interview Beyond. When they first meet Beyond, he doesn't look at them directly. They talk for a bit, and at one point, Beyond looks at Mello, seeing nothing above his head, is irritated af and asks, "………………. what did you say your name was again?" or he just starts chuckling. Mello takes this as confirmation: Beyond has the eyes. They hand Beyond the prepared Death Note papers, signaling, "we know about the Death Note; be open with us." Beyond sees Sidoh and starts laughing maniacally. What Mello doesn’t know is that Beyond has no actual knowledge about the Death Notes and won’t be giving him any answers. But IMAGINE the dialogoue possibilities— Mello going "You can see things other people can’t see, right?" "I can tell you when you’ll meet your end if you just … show me your face." Beyond lets on that he knows how to calculate the lifespan. Mello might even plan on breaking Beyond out of prison to work with the Mafia in some way. After all, Beyond is a highly intelligent maniac with The Eyes. Thouhg to avoid messing with canon too much, Beyond gets killed by Kira before Mello can make it happen. This adds an interesting side plot by just extending Beyond’s death date a couple of years.