  Heavy-flavour hadrons are recognised as a powerful probe for the
characterisation of the deconfined medium created in heavy-ion collisions, the
Quark-Gluon Plasma (QGP). The ALICE Collaboration measured the production of
${\rm D}^{0}$, ${\rm D}^{+}$, ${\rm D}^*$ and ${\rm D_s}^{+}$ mesons in Pb-Pb
collisions at $\sqrt{s_{\rm NN}}=5.02~{\rm TeV}$. The measurement of the
nuclear modification factor ($R_{\rm AA}$) provides a strong evidence of the
in-medium parton energy loss. The comparison between the ${\rm D_s}^{+}$ and
the non-strange D-meson $R_{\rm AA}$ can help to study the hadronisation
mechanism of the charm quark in the QGP. In mid-central collisions, the
measurement of the D-meson elliptic flow $v_2$ at low transverse momentum
($p_{\rm T}$) gives insight into the participation of the charm quark into the
collective motion of the system, while at high $p_{\rm T}$ it constrains the
path-length dependence of the energy loss. The ${\rm D_s}^{+}$ $v_2$, measured
for the first time at the LHC, is found to be compatible to that of non-strange
D mesons and positive with a significance of about $2.6~\sigma$. Further
evidence of a strong coupling of the charm quark to the light quarks of the
underlying medium is suggested by the first application of the Event-Shape
Engineering (ESE) technique to D-meson elliptic flow.
