A 25-year-old man presented to a major trauma centre with multiple stab wounds, most significantly to the right buttock. Triple-phase CT revealed no acute bleeding and his wounds were closed. In the month following injury, he re-presented seven times to the emergency department (ED) complaining of bleeding and wound breakdown. After his seventh ED attendance, he was examined under general anaesthesia. Intraoperatively, profuse arterial bleeding was encountered and the local major haemorrhage protocol was activated. The on-call consultant vascular surgeon attended and definitive control was achieved. A large haematoma had acted to tamponade ongoing arterial bleeding and an underlying pseudoaneurysm: a finding not reported, but present, on the initial CT angiogram. Following 24 hours in the intensive care unit, he was transferred to the surgical ward and discharged 4 days later. Regular review in the outpatient department over the following 9 weeks monitored successful wound healing.