  In this paper, we investigate the possibility of a strong first-order
electroweak phase transition (SFOEWPT) in the model `CP in the Dark'. The Higgs
sector of the model consists of two scalar doublets and one scalar singlet with
a specific discrete symmetry. After spontaneous symmetry breaking the model has
a Standard-Model-like phenomenology and a hidden scalar sector with a viable
Dark Matter candidate supplemented by explicit CP violation that solely occurs
in the hidden sector. The model `CP in the Dark' has been implemented in the
C++ code BSMPT v2.3 which performs a global minimisation of the
finite-temperature one-loop corrected effective potential and searches for
SFOEWPTs. An SFOEWPT is found to be allowed in a broad range of the parameter
space. Furthermore, there are parameter scenarios where spontaneous CP
violation is generated at finite temperature. The in addition spontaneously
broken $\mathbb{Z}_2$ symmetry then leads to mixing between the dark and the
visible sector so that CP violation in the dark is promoted at finite
temperature to the visible sector and thereby provides additional sources of CP
violation that are not restricted by the electric dipole moment measurements at
zero temperature. Thus, `CP in the Dark' provides a promising candidate for the
generation of the baryon asymmetry of the universe through electroweak
baryogenesis.
