  A K-matrix formalism is used to relate the amplitudes for the three reactions
pd --> 3He eta, pi- 3H --> 3He eta and pd --> 3H pi+. Free parameters are
fitted to the available experimental data and an extrapolation below the eta
3He threshold is made to see the origin of the eta 3He threshold enhancement.
The existence of a virtual -- and not a quasi-bound -- state finds support in
the data. The K-matrix permits a discussion of eta-pi mixing. A mixing
parameter of 0.010(5), i.e. a mixing angle theta =0.6(3) degrees, is extracted
from a best fit to the very recent pd --> 3He pi0 reaction data.
