  One or more searchers must capture an invisible evader hiding in the nodes of
a graph. We study this graph search problem; we emphasize that we study the
capture of a node-located evader, which has received less attention than edge
search. We show that in general graphs the problem of node search is easier
than that of edge search (however node search is NP-complete, just like edge
search). We concentrate on the internal monotone connected (IMC) node search of
trees and show that it is essentially equivalent to IMC edge search. For IMC
node search on general graphs we present a new algorithm: GSST (Guaranteed
Search by Spanning Tree) which clears the graph G by performing all its
clearing moves along a spanning tree T of G. We prove the existence of
probabilistically complete variants of GSST. Our experiments also indicate that
GSST can efficiently node-clear large graphs given only a small running time.
An implementation of GSST is also provided and made publicly available.
