Alfred Hitchcock, the master of this sort of storytelling, defined the difference between suspense and surprise as a matter of knowledge. If the audience doesn’t know that there’s a bomb beneath the characters’ table then you can achieve a few seconds of surprise when the bomb goes off. If the audience knows about the bomb but the characters don’t then you can achieve a whole scene’s worth of tension, as the audience wait with baited breath to see whether the bomb will be uncovered and what will happen when it explodes…
For more on this, check out my new article on maintaining suspense over at Re:Fiction. I talk about different approaches to building tension, and take the opportunity to talk a bit about The Wire.