A 12-yeаr-оld femаle hаs had a sоre thrоat for four days, clear nasal discharge, and a low-grade fever. For the past few hours, her fever has increased, and she has had difficulty swallowing even saliva. On physical examination, the patient is leaning forward with her hands on her knees, and her posterior pharynx is erythematous with asymmetrical bulging and fluctuance. A lateral neck plain film x-ray shows thickening of the prevertebral space. Select the appropriate management.