A field installable backshell connector for a shielded cable provides an EMI shield around control signal conductors and a plastic connector of the cable and also provides a mechanical terminal of the cable. The backshell connector provides a low impedance ground path from the cable shield to a connector socket. The connector socket includes a plastic connector header that is shielded by a grounded metal shroud. When connected to the socket, the backshell is abutted with the connector socket shroud to complete the low impedance ground path from the cable shield in order to shunt electrical noise introduced on the cable shield, connector backshell and shroud to ground to resist electrical interference.