Most probable cause of death: multiple organ dysfunction syndrome (MODS) from septic shock. This is the usual terminal event when a febrile patient with altered sensorium (septic encephalopathy) deteriorates with sepsis. The question is brief, so I'm assuming that is what it asks.

The usual mechanism is a dysregulated host response. It causes vasodilatory shock with refractory hypotension and tissue hypoperfusion. Lactic acidosis, ARDS, acute kidney injury, DIC and encephalopathy follow, then multi-organ failure. The altered sensorium marks brain dysfunction, which is itself an organ failure in this sequence.

If the question means death after apparent recovery: the answer would depend on the underlying cause, which isn't given. In that case the likely candidates are:

If this is from an MCQ with options, please send them, because the intended answer may be disease-specific. For example, cerebral malaria and meningococcemia (Waterhouse-Friderichsen) each have their own terminal events.

I did not open the Harrison's sepsis chapter, so the answer rests on the textbook excerpts above. A quick PubMed check of recent meta-analyses found nothing that contradicts it.