Post-splenectomy sepsis is a serious condition with high mortality rates. We present a case of a 64-year-old patient with a medical history of splenectomy who was referred to the Emergency Department with a fever, shivers, and an altered mental state. The symptoms had started twelve hours before. Upon arrival in the hospital the patient was tachypnoeic, hypotensive and febrile. Blood cultures were taken and broad-spectrum antibiotics were started. He was directly admitted to the Intensive Care Unit with severe sepsis of unknown aetiology. CT imaging did not reveal the source of the infection. A second medical history assessment revealed that the patient had engaged in play fighting with a dog two days previously, which left a superficial lesion on his arm. A Capnocytophaga canimorsus infection was deemed likely and antibiotics were switched to intravenous amoxicillin-clavulanic acid. Despite maximal support the patient's clinical condition deteriorated rapidly. The patient died from multi-organ failure fourteen hours after admission to the hospital.