Well this seems to be a relatively new map and a brand new map to me so Time_Rift was really the one that deserves credit for this walkthrough. I must warn you that this is a walkthrough, not secrets as I don't believe I came across any. Thank Time_Rift if you ever see him.

-= WARNING - THERE BE SPOILER AHEAD!!!! - WARNING =-

The map begins in a room that looks a lot like the room from the film Saw (this map is based on that film). It has a safe in the middle and objects scattered around the room. First go behind the couch that is fallen over and behind it is a crowbar on the floor. Collect it and head to the bricked wall in the second picture below.

Now hit all the bricks until you can fit through and collect the key.

Next go toward the door and stand to the side once the key has been placed into the door.

Go out the door and head right, get your team mate to boost you over the crates and then hit the explosive box to let other team mates through.

Go through the door and go up the stairs, stick to the wall before venturing up the second set of stairs as there is a trap that will kill you.

At the top of the stairs go through the door, go forward, turn left and then go to your first right. The door will open.

It will lead you into a room like this:

Inside this room there are various objects including chairs, boxes and a needle pit. You need to get the chairs and boxes down into the needle pit and stack them ontop of each other. Here is a video showing how to get items across the room, however do not aim for behind the box, aim for infront of it (Time_Rift made a mistake, shocking I know). To get down the pit move the bed. Once down the pit you need to try different keys, your team mates will know if you have the right one. The 'needles' will not kill you instantly. There is a check feature for the key, it is the door in the room (see screenshot below), also the key most likely to be the correct one is the one that says "hmmm" for the person collecting it, its in the corner. Once you find the key throw it up to your team mate (using C by default, drop item).

Key Check Door (if it disappears its the wrong key):

After doing this you can head back out and to the end of the corridor.

This will lead you to a room where one player must do an obstacle course to get the key out. It is fairly straight forward, just use jumping and ducking at  appropriate times to complete this and try not to die.

Now head back downstairs all the way back to the first door (the one with the gun) and turn right. There should be a door leading down to the basement and furnace.

Get 4 players into the furnace and pass the key along (c default, drop item in keyboard options).

Now collect a crowbar if you dont't have one. Go to the gun door and look for some crates. Jump up on the crates, there is a drop onto an electric floor trap, drop down and quickly jump to the table. Hit the table with a crowbar then go through the door (need furnace key to go through door). This will lead you to a room with valves.

One person must remain in this place. Another person must go down to the basement with the furnace and look for a vent on the side of the wall. Get in this vent (jump on the barrels, then on the box/generator/object, then on the pipe). Follow the vents relatively straight forward path, jump to float at one point.

You will land here (screenshot below), pickup the key and throw it in the glass part.

Go over the wire fence by going under the wood that looks like ladders and climbing the wire fence. Next you will need to repeat throwing the key into another section.

The key should be collected by your team mate. Note: There is a bug where the 'doors' do not open, if that happens just keep trying, it is not you or your team mates fault (It is possible to glitch if a person stands close to the glass where the key drops). After the key has been collected get your team mate to boost you out of the room and head to the stair case.

This is the final room and a damn hard one. There are some boxes you can use as blockers for the spinning blades. However you and a team mate must  slowly edge it over to the spinning blades using the ramp to 'fire' it onto your team mates head and then edging it. Alternatively you can attempt to find your own way to get the box to the blades. It is possible to block the blades with the boxes and it is also possible to jump the blades without blocking them but a lot harder. The decision is yours.

Ramp for boxes:

After the blades there is a key the you need to take back to the very first room and put in the safe. Once this happens you (or the person who put it in the safe) will spawn in a glass coffin where he must break free and get a boost to break a grate in the middle of the room with two closing walls.

Follow the vent above the wire grate for the ending.

That is the end of Saw_Beta. Hope you enjoyed this walkthrough.