So saying, she hobbled off with busy fear. The lover's endless minutes slowly pass'd; The dame return'd, and whispser'd in his ear To follow her; with aged eyes aghast From fright of dim espial. Safe at last, Through many a dusky gallery, they gain The maiden's chamber, silken, hush'd, and chaste; Where Porphyro took covert, pleas'd amain. His poor guide hurried back with agues in her brain.
Angela comes back and leads Porphyro to Madeline's room, terrified the whole time that somebody's going to catch them.
Finally, they reach Madeline's room, which is quiet and "chaste." It may seem funny to personify a room, but you can think of it as both setting the mood and as also describing Madeline herself, a virgin.
Porphyro hides himself and is super-happy about things ("pleased amain"), while poor Angela comes in, in a fair amount of distress (the "agues" in her brain refer to shivering or fluttering from illness).