A convertible device that converts between an activity mat and a storage container to capture and store numerous articles. Upon reclosing the activity mat, the articles are recaptured into the storage container. The device includes walls and a base, webbing connected between each adjacent wall pair, and a joint connected between the base and walls so that they are foldable into a third configuration wherein the footprint of the folded device is roughly the size of the base. In the third configuration, the walls are stacked relative to the base. The convertible device may further include attachment means for releasably holding the walls in a rigid and upright position in the first configuration. The webbing can be inwardly biased such that when the walls are urged from the second to the first configuration, the webbing folds toward the interior of the convertible device.