Dropping the ball from the kick off was not what the start Waghi Tumbe were looking for.
It cost them with a penalty conversion from Jefferey Para and then later a try to John Horope that put Isou in front at 6-0 inside 10 minutes.
But Tumbe grouped and hit back through a Frank Kagai four pointer which was converted to even the score.
Ball handling was an issue for Tumbe and Isou made them pay twice with Horope bagging his second, followed shortly after by Isou's other centre, John Stanley.
With both tries left unconverted, the men from Waghi only needed a try to put themselves back in the contest.
A converted try minutes from half-time did exactly this to leave Isou trailing 14-10 at the end of the first 40 minutes.
The elusive Horope gave Isou some breathing space early in the second half when he scooted over to make it a hat-trick for the afternoon.
Tumbe didn't go down without a fight and with two quick tries, the score was put to 20-18 with 10 minutes left on the clock.
But it was not to be with Wilfred Martin putting the nail in the coffin crashing over out wide to seal victory for Isou.