First edition

Don't Look Back is set in a world full of conspiracies and unexplained phenomena.

Players take on the roles of agents working for a secret government agency investigating supernatural and paranormal events.^[1] Players begin by creating a character with six abilities and about ten skills. Each of a character's abilities and skills has a rating from +5 to -5, with 0 representing an average ability or skill.^[1]

Skill checks are done by rolling at least three six-sided dice, with a roll of 11–18 always a success, and a roll of 10 or less always a failure. The total number of dice the player throws is calculated as 3 plus the absolute value of the sum of bonuses or penalties from the most relevant ability, most relevant skill, and the difficulty of the task. If the Base Total of those three factors is above zero, the player totals the three highest dice. If the Base Total is negative, then the player uses the result of the lowest three dice. For example, two characters want to scale a wall that has a difficulty of -2:

• The first character has a -1 Fitness ability and +5 Climbing skill. These combined with the wall's difficulty of -2 gives a Base Total of +2. The absolute value of 2 is added to 3 resulting in a total number of dice to be thrown of 5. Because the Base Total of ability + skill + difficulty was above zero, the player would use the result of the three highest dice to determine success or failure.
• The second character has a +1 Fitness ability and +0 Climbing skill. These combined with the wall's difficulty of -2 gives a Base Total of -1. The absolute value of 1 is added to 3 resulting in a total number of dice to be thrown of 4. Because the Base Total of ability + skill + difficulty was below zero, the player would use the result of the three lowest dice.^[1]

The same single roll system is used in combat. An attacker determines how many dice to throw; if successful, the number of points of damage is calculated as the dice total minus 10, the sum then multiplied by the weapon's damage modifier and any resistance modifier of the defender.^[1]

Second edition

In the second edition, a more light-hearted approach is taken to the horror theme. Characters are now ordinary citizens who are pulled into investigating unusual events by circumstances.^[2]

Characters have seven abilities, with ratings from +4 to -4. Depending on the character's background, the character also receives a number of acquired abilities. The player can spend a fixed number of points on either improving abilities or acquiring additional abilities. The player can also spend points on buying Advantages such as Ambidexterity; and receive a refund of points for buying Disadvantages such as Gullible. There is no limit to the number of Advantages and Disadvantages that can be purchased, as long as the total expenditure of points is zero.^[2]

The skill check resolution system is identical to the first edition except that the final result of the dice roll is checked against a Quality Table to resolve the attempt, which can be anything from Horrible Failure to Incredible Success. The gamemaster then adjudicates what happens as a result.^[2]

The combat system uses the same single dice roll system to determine success or failure; resultant damage is calculated by multiplying the action's Quality Rating with the relevant Defense Scale factor. The result is rounded down, resulting in the amount of damage applied. ^[2]