rob had worked with impatient zeal and moderate skill and had successfully negotiated the obstacles caused by the zip of janets anorak , the weight of her thick jumper , several buttons on her blouse , and had just worked his hand through the multitude of layers to be able to feel the thin , silky material of the cup of her bra and the reassuringly hardening protuberance beneath , when he was halted in his exploration by the sudden , deep , throaty cry which rent the air with a terrifying note of anguish .