Mission 46 - Rescue Ralph McNairy
First glance at this brick building shows Ralph and a whole lot of sentries.
You can get in through the west by jumping up on a dumpster and over the north side of a brick enclosure here, to get at a locked door. Sneak through the brick passage, into the meat locker and past 'Rocky.'
Whistle over the guards from the next room (with the conveyor belts), including a sentry. From here, standard whistlekill procedure applies- there's a good spot near the trussed captive on the east side of the ground floor, which has crates north and south for multi-angle luring.
Take out passersby, then grab the tac vest from the weapon locker indicated on the minimap. Here you'll also find some cash and Barker shotgun, if you need ammo. Cornerkill anyone else on the ground floor you might have missed, then head up the stairs in the northeast corner.
Break up the conversationalists, advance (grabbing a medkit on the wall if you need it), and take out a guard and the last sentry. This leaves one guy guarding Ralph- take him out anyway you please.
Before rescuing Ralph, you might head south to clean out the office of its excess cash
Collectible Alert: Vargas painting
After that, it's time to do what you came here for- cut Ralph free and end the mission. He'll skeddadle, but you may want to stay and follow your minimap to the remaining cash stacks and medkits around the building- there are plenty. If you've been following this walkthrough in order, that should be enough to trigger the next conversation with Bear to get Sonny.