The study deals with the presentation of a new metamorphic parallel mechanism that has the ability to change mobility in a wide range. Based on the newly invented reconfigurable hook joint with two distinct phases, the constraint forces are altered to be exerted on the platform. This change of constraint forces result in change of mobility of the mechanism and therefore degree of freedom of the platform. This work requires screw system analysis and by identifying both motions screw system and constraint screw system, the topological configurations with the variable mobility. The phenomenon of bifurcated motion of the mechanism in its low-mobility configurations is to be investigated based on constraint analysis.