Books in the Cassandra Virus series

Something is cutting off Spohrville's communication with the outside world. The phones don't work. There's no radio, no TV -- no internet. Are eco-terrorists trying to shut down the Mars Relay satellite? That's what the government says, but Jordan and Helen and the sentient virtual supercomputer Cassandra don't believe a word of it. The town is overrun with "birdwatchers" who can't tell a hawk from a heron. Jordan's old enemy, Harvey Number Two of the spy agency Bureau 6, is sneaking around pretending to be a cop on holiday. And archaeologist Uncle William has dug up a very strange black rock while excavating an Acadian settlement. With no land-lines to the site of the dig and wireless communication impossible, Jordan and Helen have no back-up from Cassandra. They've taken on corrupt government agents and industrial spies before, but they've always had Cassandra behind them. It's the twenty-first century. The bad guys have night-vision goggles and interference triangulators. How did Jordan and Helen get stuck with a bunch of musket-toting historical re-enactors as their only allies?