Here's how to downpatch your game to v1.0.5.
1. Open the Steam Console (choose the easiest for you):
2. Paste the following command into the console and press Enter:
The steam console will start downloading the patch, however it will give you no indication of progress so you will just have to wait it out. Once it is finished, the console will print out a line that says something along the following:
3. Open the folder specified by the console and copy everything inside.
4. Navigate to your TSWSM installation directory (\Steam\steamapps\common\The spy who shot me™) and:
5. Paste the depot files into the installation directory.
6. Exit Steam.
7. Navigate to your steamapps folder (\Steam\steamapps), look for appmanifest_771810 and open it in a text editor:
8. Save the file and re-open Steam. You've successfully downpatched your game!
Note: You may need to repeat step 5 whenever future updates happen.
To undo all of this, simply navigate to your steamapps folder (\Steam\steamapps), delete the appmanifest_771810 file and restart steam. As a disclaimer, I suggest you delete the game folder as well and let Steam download the game from scratch.
Let me know if anything if you have any questions, if anything needs to be changed or anything's not working for you.