Abstract: A door latch mechanism includes a housing having a bolt extending outwardly therefrom, and a split sleeve extending through the housing and disposed to drive adjacent cams concentric with the sleeve to operate a retractor to retract the bolt against a biasing spring. The split sleeve receives a split spindle of a door knob assembly to rotate the sleeve and retract the bolt. A locking adapter includes a generally cylindrical housing having a chordal slot for receiving the latch housing therethrough. The cylindrical housing includes aligned apertures through which the spindle extends. A locking cam is secured in one aperture, and a lock release cam is secured in the other aperture. A lock shaft extends through the housing parallel to the axis of the apertures, and includes a boss for engaging and blocking the locking cam to lock the spindle, and a protrusion engagable by the release cam to drive the lock shaft axially to release engagement of the boss and the locking cam.