The question below consists of a set of labelled sentences. Out of the four options given, select the most logical order of the sentences to form a coherent paragraph.

P. Celts believed that on the night before the new year, the boundary between the worlds of the living and the dead became blurred.

Q. Halloween's origins date back to the ancient Celtic festival of Samhain.

R. The Celts, who lived 2,000 years ago, mostly in the area that is now Ireland, the United Kingdom and northern France, celebrated their new year on November 1.

S. This day marked the end of summer and the harvest and the beginning of the dark, cold winter, a time of year that was often associated with human death.