GUMSHOE is a hybrid system. On the one side are the fundamentally GUMSHOE investigation abilities. These allow you to get information without a random test to see if you find the book in the library, or decode the encrypted document. They also allow special benefits, which can interact with the other side of GUMSHOE – the General ability side.
When you make a die roll you can spend points from your General ability to increase your chance of success, and if you have enough points, succeed at that task. GUMSHOE characters in most settings are pretty competent, and when it matters, they succeed. However, there is nothing findamental about GUMSHOE which means characters have to succeed. – GUMSHOE doesn’t care whether random tests are succesful or not.
There are some settings where the chance of failure is a fact of life. For example, in a post-apocalyptic setting, gear is unreliable and floors give way unexpectedly. This option reflects that type of setting. It’s also an option for any group which takes umbrage at the principle of automatic success on certain tests. My home group has recently been playing such a game, and we have a mixture of spendthrifts and point-hoarders, and the hoarders are certainly happier. I, however, am learning to live with unexpected failure in a GUMSHOE game.
The idea is that your spend on any test is capped according to your rating in that General ability.
The option also ensures that characters with higher ratings get to succeed with certainty where others might fail. If you have a suitable Investigative ability, you can use it to add extra points to your roll on top of the cap – so knowledge can increase your chance of success. This is usually three points for a clearly appropriate spend.
Let’s say you have a Sneak rating of 4, and you are trying to get past a tough security system. You can spend one point of Sneak on your roll for the Sneak test. You could supplement that by spending a point of Architecture to find a hidden route – so you can add four points to the sneak test in total.
You can still piggyback (spend a point to join in with someone else) or cooperate (spend points on each other’s rolls if it’s appropriate)
Some tests require post – success spends (eg thriller options). There are two approaches here: the first is to enforce the additional point spend only if the test succeeds. The second is to enforce the point spend whether it succeeds or not. I think the former is more appropriate for settings with restricted point spends.
I suggest for this option to work, you restrict the top Difficulty number to 6, to allow near certain success for very able characters.