One example is the arrival of Osembega at Mama's the first time. At this point he is willing to unload his weapons and leave the ammunition at the door so that even if he gets upset, no one will get killed. During his later visits, this will change, but this visit serves to heighten the tension and foreshadow later conflict in the establishment.
A second example is when Christian appears to announce that the white pastor, who was suspected of aiding the rebels, has been brutally murdered. This demonstrates the rising danger to everyone around but also the lengths that Osembega is willing to go to to see revenge against those he perceives as his enemies.
A third example comes when Osembega arrives in Mama's for the second time and he demonstrates his desire to be with Sophie. Her response of unwillingness and her demonstration of this by spitting on him drives the tension to new levels suggesting perhaps that the climax is soon to arrive.