A pattern (n) - the way in which something happens or develops (The illness is not following its usual pattern).
A tissue (n) - (a piece of) soft thin paper.
Vehicle (n) - something in or on which people or goods can be carried, esp. along roads.
Liaise (v) - to work together so that all the people are informed about what is being done.
P.C. - Police Constable; a male member of the police force having the lowest rank.