The route Isis at Swanage has an error in the 2012 guide that has been causing a few people to go off route. A slightly clearer route description is below:
A popular route with varied climbing in good situations. Start at the left-hand side of a high, arched recess 5m right of a large block. Climb the groove on the left until a move left gains the lip of an overhang. Pull up slightly left then back right into a bulging groove. Climb this to finish up two short walls.
The correct topo line is below: