  Using Monte Carlo simulations we show that the autocorrelation function
$C(t)$ in the d=3 Ising model with a plaquette interaction has a
stretched-exponential decay in a supercooled liquid phase. Such a decay
characterizes also some ground-state probability distributions obtained from
the numerically exact counting of up to 10^450 configurations. A related model
with a strongly degenerate ground state but lacking glassy features does not
exhibit such a decay. Althoug the stretched exponential decay of C(t) in the
three-dimensional supercooled liquid is inconsistent with the droplet model,
its modification that considers tensionless droplets might explain such a
decay. An indication that tensionless droplets might play some role comes from
the analysis of low-temperature domains that compose the glassy state. It shows
that the energy of a domain of size l scales as l^1.15, hence these domains are
indeed tensionless .
