The light, huh? Sounds shitty, much like every other damn thing about this mushi situation ... and if Childermass is unlucky, Ginko's response is going to be much the same as before: wait it out. Lambert glances around them, frowning slightly. If light is the problem, at least, sticking around the lakeshore much longer isn't going to do the magician much good. He can't really communicate that effectively with touch alone, but if Childermass won't move his arm from his face, Lambert will reach for his other hand instead.

If the magician will permit, he'll pull his fingers to clasp his shoulder, insistent, body already turning away from the lakeshore. If that's not enough of a hint, maybe the hand the witcher puts to his back, pushing him to take a step forward, will do the trick.