Sensing with undetected photons enables the measurement of absorption and phase shifts at wavelengths different from those detected. Here, we experimentally map the balance and loss parameter space in a nondegenerate nonlinear interferometer, showing the recovery of sensitivity despite internal losses at the detection wavelength. We further explore an interaction-free operation mode with a detector-to-sample incident optical power ratio of over 200. This allows changes in attowatt levels of power at
3.4
μ
m
wavelength to be detected at 1550 nm, immune to the level of thermal black-body background. This reveals an ultrasensitive infrared imaging methodology capable of probing samples effectively “in the dark.”