  We report the discovery of a mid-infrared (MIR) flare using WISE data in the
center of the nearby Seyfert 1.9 galaxy MCG-02-04-026. The MIR flare began in
the first half of 2014, peaked around the end of 2015, and faded in 2017.
During these years, energy more than $7\times10^{50}$ erg was released in the
infrared, and the flare's MIR color was generally turning red. We detected
neither optical nor ultraviolet (UV) variation corresponding to the MIR flare
based on available data. We explained the MIR flare using a dust echo model in
which the radiative transfer is involved. The MIR flare can be well explained
as thermal reradiation from dust heated by UV-optical photons of a primary
nuclear transient event. Although the transient event was not seen directly due
to dust obscuration, we can infer that it may produce a total energy of at
least $\sim10^{51}$ erg, most of which was released in less than $\sim$3 years.
The nature of the transient event could be a stellar tidal disruption event by
the central supermassive black hole (SMBH), or a sudden enhancement of the
existing accretion flow onto the SMBH, or a supernova which was particularly
bright.
