Plump the raisins in hot water to cover about 15 minutes. Drain well, reserving the soaking liquid.
Heat the garlic in the olive oil for a minute or two just to remove the bite. Let cool.
Combine the raisins, garlic with oil, cucumbers, yogurt, mint, and walnuts in a mixing bowl. Season to taste with salt and pepper. Add the raisin soaking liquid to taste for a pleasing balance of sweet and tart. Serve at room temperature or slightly chilled.