The Dam Across The Stars

Humankind finally achieves a method of space travel that enables them to explore our galaxy. However, whilst on a routine transport mission, a cargo ship 'folds space' too close to a planetary body causing a catastrophic accident and ends up projecting itself to the furthest reaches that its drive allows. Upon materialising in normal space the crew find themselves confronted by an impenetrable barrier which ultimately becomes known as The Dam.
Humankind wonders whether this dam is meant to keep something out, or us in, and soon ships of all kind begin to search for a way through. Planetary authorities decide to set a quarantine zone around the barrier and a new breed of human is formed. The Sentinels, they are genetically adapted to survive the loneliness and rigours of patrolling such a vast area. Two such Sentinels are involved in a re-entry burn-up, one manages to download his memories so that he can be re-trunked in time, the other doesn't and has to hand in his commission (not an easy thing for someone grown for one purpose only) he goes rogue.