It's surprisingly simple, actually.

The bariet takes a pull at the fumbler, and then one of two things happens: Either he misses, or hits it (towards the flange or along the foul line to the base). There are three spichies who can try to deflect the fumbler, either towards the simulcum or out to the field.

The simulcum is the more audacious play, giving an instant spiel if they succeed in darving the bariet. But it runs a serious risk of a spurn, so unless a spichie is particularly strong, the field is the safer play.