Fast rerouting requires that a backup route is already available at each node so that traffic can immediately be shifted on it without new path discovery and convergence time delay. Handling multiple failures with least possible delay, high throughput and least overhead with regard to memory and battery is a real challenge in Wireless Sensor Networks (WSN). Current fast rerouting techniques that handle multiple failures do not specifically target mission-critical WSN applications. Fast Rerouting techniques use spanning trees, backup topologies or configurations to shift traffic immediately as and when error is detected. These techniques do not focus on finding least hop count on the backup path and therefore, end-to-end delay on the backup paths is higher than on the primary path. The proposed Fast Rerouting Protocol (FRP) establishes primary and backup routes before the start of data transfer. It creates at least one backup path towards destination from every node on the primary path. FRP therefore has the ability to handle multiple failures in mission-critical WSN environment. NS-2 simulation results of FRP against the competitor reveal that, FRP takes least time and control messages to establish shorter fast rerouting paths, produces minimum end-to-end delay, least energy consumption and higher network life time.