What if everything that went wrong on "A Red Letter Day" was not caused by what you thought? What if your teleport ripped a hole in space and time? Now you must travel through time to correct the events and set right your past.

Causality Effect
A Red Letter Day Gone Wrong

  • View media
  • View media
  • View media
  • View media
  • View media
  • View media

Causality Effect has been updated. I have fixed and changed little bugs found in the mod after its release. In other news the mod will be aired in PC Games magizine this month and will be on a DVD disc that comes with your magizine.

Causality Effect
?A Red Letter Day Gone Wrong?

The installer

8 years ago Full Version 4 comments

Download me to install the game

The Video Trailer

9 years ago Movies 0 comments

Check out the trailer with in game footage.

Post comment Comments  (10 - 20 of 76)
kalidrone Jan 1 2011 says:

Extremely amazing idea and story, I LOVE IT, no lie! X3 Can you please tell me if there is a way to save Eli, Barney or Kleiner? I'd truly appreciate it. :)

+1 vote     reply to comment
kalidrone Jan 1 2011 replied:

Help me out here, from what I see on the comments here you can kill either Alyx/Breen at the ending scene but when I get there I have no weapons to kill them with, please tell me how to kill either because after Gordon exits the Teleport room I try to rush kill breen but it's like he isn't even receiving anything from what I fire at him, please help me out here, please. D:

+1 vote     reply to comment
kalidrone Jan 6 2011 replied:

YES! I managed to get the different endings! Now I know how to get them as well! X3 To all who are looking for the different endings in this story: Please be advised that after your brief meeting with Gman you should HIGHLY take heed of his Very Words because right when you load into the rooftop battle Alyx Vance and Wallace Breen make a break for it and it's up to you to see who you will kill be be warned as there are some deadly Combine Elites loosely guarding them but there's only around 2-3 at most and THAT's when you can decide what ending you want, just wanted to say this for all of you frustrated and confused on how to get the different ending as I was, truly! XP lol So you must move with as much haste as possible while staying alive from the Combine Elites while taking either Breen/Alyx out, good luck. :)

+1 vote     reply to comment
kalidrone Jan 6 2011 replied:

Also I just want to say that this reminds me A LOT of Breakdown with Derrick changing the time line, so this is such an awesome story, thank you for this, it has made me very happy. XD

+1 vote     reply to comment
superstepa Nov 22 2010 says:

Doh , In the beginning , when there is a combine door , and a combine "Plane" flies , I alwayshet killed , because this rebel CANT KILL THIS DAMN THING

+1 vote     reply to comment
megaman951 Sep 4 2010 says:

hmmm when I start the mod Alyx just stands there...I assume this is because of the huge update they did to HL2 ?

+1 vote     reply to comment
MizoreJedi Jul 19 2014 replied:

The same thing happens to me, when I write the first map in the console, because if I go to New Game, the game returns to the menu.

+1 vote     reply to comment
ninjatwork Jul 4 2010 says:

This was one of the best mods I've ever played in respect to the HL2 story line. I don't even know what else to say other than that I gave it a 10.

Oh, and I appreciate the small download size too. =D

+1 vote     reply to comment
johnnyB96000 Jul 6 2010 replied:

Did anyone notice that if you draw in a Big black zombie thing into a barnacle the game always crashes, i guess this is due to the fact there is no sprite or sequence in the game so as to which the zombie dies in this way. Nor is there in HL2 to my knowledge

+1 vote     reply to comment
Rallymen007 Dec 25 2009 says:

Just finished this mod, and I really enjoyed playing. Mapping is nice, cut scenes are good, but the timeline is kind of weird, all those teleports confused me :)

But, how do you get other endings ?

+1 vote     reply to comment
ig Feb 28 2010 replied:

Yuo kill breen or alyx or both or neither

+1 vote     reply to comment
PsiKO911 May 13 2010 replied:

OK but how do you kill them?

+1 vote     reply to comment
johnnyB96000 Jul 6 2010 replied:

you just run up to them at the last scene and shoot them with a shotgun as quick as possible, both one or the other or none gives 4 possible endings.

+1 vote     reply to comment
Post a comment

You are not logged in, your comment will be anonymous unless you join the community. Or sign in with your social account:

Half-Life 2
Send Message
Release date
Released 2007
Mod watch
Start tracking
Community Rating



101 votes submitted.

You Say


Ratings closed.

Embed Buttons
Link to Causality Effect by selecting a button and using the embed code provided more...
Causality Effect
Last Update
8 years ago
92 members