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Cataclysmic Variables (CVs) are semi-detached binaries composed of a whitedwarf orbiting a lower-mass K or M star. We investigate whether CVs areresponsible for a new intriguing feature (the `hook') that appears in the GaiaDR3 colour-magnitude Hertzsprung-Russell diagram (HRD) when selecting sourceswith low extinction. We also aim to understand the location of CVs in the HRDbased on the predictions of the disc instability model (DIM). The DIM is thefoundation on which rests our basic understanding of stable (novae-like) andoutbursting CVs (dwarf novae). We calculate the expected behaviour of CVs inthe Gaia HRD taking into account the variable light contributed by theaccretion disc, the companion, the white dwarf, and from the bright spot wherethe Roche lobe overflow stream from the companion intersects the disc. We findthat the `hook' feature is most likely to be composed of CVs. The `hook'corresponds to the limited region where stable CVs (novae-likes) must belocated in the HRD according to the DIM, with the bluest systems having theshortest orbital period. Unstable systems, giving rise to dwarf novaeoutbursts, trace counterclockwise loops in the HRD. The overall behaviour isconsistent with the location of the various CV subtypes in the HRD. Theseresults can be used as a basis to pinpoint interesting outliers in the HRD,either due to their location or their tracks. These outliers may signal newsubtypes such as cold, stable CVs with truncated discs, or may challenge thedisc instability model.

Cataclysmic Variables and the disc instability model in the Gaia DR3 colour-magnitude diagram