SENTINEL is the second book in Orsus Series Two, The Immortals Matrix.

1917

Beneath the mud of Messines Ridge, something far older than the First World War is being discussed in the dark.

The system no longer needs to return home.

Earth itself becomes the experiment.

In 1992, the Mangonel gathered once more inside the Chrysler Building. Simon de Montfort watches Manhattan from thirty-two floors above the city while the oldest financial reserve in history remains hidden behind eight centuries of silence.

Meanwhile, the Equis Bellici closes in.

From the mines beneath Flanders to the siege engines of Montségur... from the curse of Jacques de Molay to the strange sanctity surrounding Padre Pio... from Washington's marble walls to hidden rooms beneath New York... SENTINEL expands the hidden architecture behind the ORSUS universe and reveals the operational origins of a conflict centuries in the making.

Some systems survive because they are protected.

Others survive because nobody realises they are still there.